Really, any computer will work. I recommend:

2 Cores in the CPU - Concurrency will be better if you can actually see speedup. Quad core is definitely the best however.

A dedicated video card - Even a cheap one will be miles ahead of an integrated GPU.

RAM - I recommend 8 GB, simply because it can handle pretty much *anything*.

Any HD, except aim for a big amount of space.

Pretty much any OS. I recommend you get windows and learn how to Dual Boot Linux. Than you can learn how to use Linux while having another OS to use when you can't get Linux to work.

Display - 1920 x 1080 Pixels is ideal.

I recommend (for programming):

A quad core intel processor (I5 or I7).

A Nvidia graphics card (simply because so many games are made optimized for them, and I just like them). Preferably gtx 750 or above.

8 GB of Ram.

Windows 8, then Dual Boot Ubuntu onto it.

Keyboard / Mouse - As a programmer, you'll be typing alot. Get a good one if you have money to spare. If you think you won't need a good one, put the money into your video card. It's really a luxury.

Most of the other Odds and Ends don't really matter as much.

This is not true not every PC will work, it all depends on context in work a dual core machine without an SSD would not do for me, asset builds would be 1.5 hours instead of 0.5 for example. Same goes for the RAM department the more you have the better, I tend to have 20 windows open at the same time, sometimes up to 3 instances of Visual Studio and I don't turn it off for 5 days.

As far as GPU's go in a professional setting you should have both an AMD and NVidia card so you can test on either, any DX11 card at the moment will do.

Screen space is up to you but I do recommend full HD screen at least, I have 2, 24" monitors at work one for code the other for debug windows.

I make tripple A games so a high end machine is pretty much what you want to have in those cases, in the case of home brew I have a slightly less powerfull machine at home but not by that much if you take in how old it is.

Don't buy a full assembled desktop from best buy or wherever. You can get way better parts for better prices by ordering them from New Egg and putting the system together yourself. It only takes a few hours and it is really worth the effort. It may seem really cool to have the tons of cores that AMD offers, but honestly an Intel quad core is considerably better than an AMD 8 core, just from what I have seen from 3 of my friends recently building computers. Don't skimp on the fans and heat sinks. Keeping your CPU cool will help it last longer.

Here are my specs. This computer works fairly well, but it is getting a little old and slow.

It is a Dell Dimension E521 that I made a few upgrades to.

64 bit Athlon dual core

8gb ddr2

500gb HD

$50 evega/nvidia graphics card(spend at least $75 in this department)

windows 7/linux mint

I'm using a Macbook Pro for iOS development. Everything else is on my dev desktops, which have Core i7 CPUs, 16 GB or more of memory, SSDs, and recent GPUs (GTX 470, GTX 690, GTX Titan, HD 7870, HD 7970, etc). For development pretty much any CPU will do, quad core or better ideally. My main criteria are tons of memory, and a full featured GPU from NV or AMD. No Intel chips for development -- their GL implementation is way too glitchy. NV is probably the best for multi-faceted dev work. SSD is very nice to have but not mandatory.

8 GB of memory on the Mac is barely enough, and I'm just doing iOS work. But OSX is an extremely memory hungry OS, and the combination of XCode and LLVM/clang also consumes unbelievable amounts of memory. Even so, memory's cheap enough that it's worth going straight to 16 on a desktop. 8 is probably ok on laptops.

Screens are personal preference but the more the better. I'm running dual 27 (2560x1440) or triple 23/24 (1920x1080 or 1920x1200) setups nowadays. But it's not critical to lay out tons of cash here.

If you're going to college/university this fall, then it's probably a good idea to go for a laptop. Otherwise, I'm a big desktop fan.

For any computer, keeping everything (not only software!) on a good SSD drive will accelerate development because compared to an hard disk it will speed up common activities by a ridiculous factor:
 
- text search across many files (e.g. find and grep)
- software installation and reading/writing archives of many files
- access to large numbers of files in general
 
For desktop machines in particular, enough video outputs for your multiple screens, which should be two Full HD ones at a minimum. Having two or more full-screen things to watch is normal:
 
- an art/authoring tool or code editor and the game
- a debugger or realtime monitoring tools and the game
- multiple instances of the game (for comparison or multiplayer testing)
- some kind of editor and reference documents or images
- something you are concentrating on (editor, documents) and notifications to look at occasionally (chat, long-running console programs, email clients, etc.)

Don't forget, as well as an uber rig, to buy an older Thinkpad (X61) or Dell laptop with an integrated (possibly Intel GMA 9xx) graphics card to test your games on. Not only does this give you a feel of how your game might run on a typical tablet, it also allows you to test your game on the (admittedly lowest common denominator) of computers that people (especially in the casual market) still use!

Really, any computer will work. I recommend:

2 Cores in the CPU - Concurrency will be better if you can actually see speedup. Quad core is definitely the best however.

A dedicated video card - Even a cheap one will be miles ahead of an integrated GPU.

RAM - I recommend 8 GB, simply because it can handle pretty much *anything*.

Any HD, except aim for a big amount of space.

Pretty much any OS. I recommend you get windows and learn how to Dual Boot Linux. Than you can learn how to use Linux while having another OS to use when you can't get Linux to work.

Display - 1920 x 1080 Pixels is ideal.

I recommend (for programming):

A quad core intel processor (I5 or I7).

A Nvidia graphics card (simply because so many games are made optimized for them, and I just like them). Preferably gtx 750 or above.

8 GB of Ram.

Windows 8, then Dual Boot Ubuntu onto it.

Keyboard / Mouse - As a programmer, you'll be typing alot. Get a good one if you have money to spare. If you think you won't need a good one, put the money into your video card. It's really a luxury.

Most of the other Odds and Ends don't really matter as much.

This is not true not every PC will work, it all depends on context in work a dual core machine without an SSD would not do for me, asset builds would be 1.5 hours instead of 0.5 for example. Same goes for the RAM department the more you have the better, I tend to have 20 windows open at the same time, sometimes up to 3 instances of Visual Studio and I don't turn it off for 5 days.

As far as GPU's go in a professional setting you should have both an AMD and NVidia card so you can test on either, any DX11 card at the moment will do.

Screen space is up to you but I do recommend full HD screen at least, I have 2, 24" monitors at work one for code the other for debug windows.

I make tripple A games so a high end machine is pretty much what you want to have in those cases, in the case of home brew I have a slightly less powerfull machine at home but not by that much if you take in how old it is.

This wasn't intended for someone who Made Triple A games and will be building large codebases. I think if he ever gets to that point he will know more than enough to get a good computer.

I'm bouncing you all to the lounge. This isn't really a relevant discussion for the For Beginners forum.

Its nearly impossible to buy a new desktop or laptop computer that would be too under powered and painful to develop on that it was a non-starter. Heck, its hard to find a machine even 2-3 years old that would be, unless you dipped down into a netbook or something.

My current desktop is probably 4 years old now, Its a core 2 duo with a slight overclock to 3.6Ghz, 8 Gigs DDR2, with a 256GB SSD and Radeon 6990 (which were at the time my two most expensive components), and both strictly unnecessary for game development. In every respect but graphics its actually much slower than my laptop (which is where I do most of my real work these days). But its more than comfortable for programming.

You can very easily build a complete desktop with very good performance for around a grand. Say, a quad-core i5, quality motherboard, 8-16GB RAM, modest SSD + sizable HDD, and a very capable GPU (I saw Radeon 6970s a week ago for $180 -- granted its a silicon generation behind, but its still DX11.1 and very powerful). Depending on component selection you might even get a keyboard, mouse, and a 1080p monitor or two without going much over budget.

You could scale back to even around $500 and still have an eminently capable computer, with mindful component selection.

Its pretty easy to get a very capable laptop with dedicated graphics for under a grand too, like this one.