Is the source code to Popnfresh's MD3 exporter available anywhere? That tool has proved vital to my development over the past few years and now that I plan on making a couple of custom extensions to the MD3 format for custom hitbox storage, it would really be useful if I could make it recognize the proper object names and not surround my models in lots of big gray blocks. :P Failing that, Discreet's website is useless, where on there can I find the MAX SDK?

It's been a while since I've worked with 3DS Max (thankfully), but I seem to remember the SDK is on the install CD with the application. The debug libraries/runtime is a separate download, but only available via the registered developers board (I think).

If you have the Max install CD then you should have it on there.

The SDK should be on the install CD however if you have 5.1 or 4.2 or maybe lower I didn't check you can grab the sdk from here
http://www.discreet.com/support/max/download/download.php3#3ds max 5.x English
(its early sorry no clicky)
you can also get the chracter studio sdk from here also, which you might need if you are doing characters but not necesarily. The maxSDK is not the greatest, but it does have some helpful examples also. Or if you are really insterested you could try to find MAXScript & the SDK for 3D Studio Max. It is basically on maxscript, but has some info on the SDK about the only book out there. It is also dated, most source is for 3dsmax r3 or 4 but I easily changed it to compile with 5. You can also look into the appwizard for Visual c++ up to r5 is supported for VC6 6 and 7 have appwizards for VC 2003

sparks.discreet.com (i think, again its morning) is a decent resource