Set deadlines, be consequent(three strikes and you are out). Make them understand that this is also a REAL job and the goal is to deliver. No linger, no unnecessary delay. Make sure that people sign a group agreement where it is written clearly that if one gets delayed he lets the whole group down.

You need to find people who are utterly loyal to the project and can deliver. If you do not want to demand this of the group then this is not a project, then this is playing around and having fun(that can be acceptable too).

Make sure that people get to work with what they like at most(or second most). Make a list of what needed to be done and make people write them on that list in first priority, second priority etc. Then roll a dice or something(or pick the best man for the job).

Do something else than just working together if possible in order to create friendship, team spirit and loyalty among the members in the project.

A group of devs. are only as strong as the weakest link. Tell the people that do not deliver on deadline that the first time, warn them the second time and the third time they have proven that they do not wish to contribute. That is what is needed to be done with people who constantly delay or don't make the deadlines(of course the deadlines has to be realistic).

I have seen way too many groups ending up with like 50 percent of the team members doing all the grunt work while the other halve barely lift a finger(horrible). Be consequent as this is your life and your time that are passing by.

do YOU have any advice for us from your own experiences that kept your team motivated, or at the very least kept the work interesting?

Yes. See the thread "How to reinvigorate a team?"
It's here in the Production and Management forum (where your post has been moved).

Check out this book, The War of Art (this is not a referral link, I don't do such things). The book is all about getting over one's resistance to work so one can get back to being productive. Also, check out Getting Things Done, a veritable cookbook of productivity enhancing practices.

But really, it all boils down to establishing a routine. Setting deadlines works for some people, not others. For me, I have to set start-on times, the complete opposite of deadlines. The next item's start-on time is essentially the deadline for the previous item, but it becomes more of a motivational piece for me to finish today's stuff so I have a clean slate to work on tomorrow's stuff.

Don't work only when you feel like it, and don't work for as long as you feel like it. If you work only when you feel like it, you will work sporadically, and if you work as long as you feel like, you will work too long, completely screwing up your schedule for everything else, which will become a subconscious deterrent to getting back to working again.

Motivation isn't a magical muse that rests on your shoulder and whispers in your ear. It's the iron rod of determination of will, beating your sorry ass into shape. For me, it helps a lot to think of it in the terms of The War of Art, defining lack of motivation as a sinister, paranormal force called Resistance. When I feel Resistance taking hold, I know it's a demon trying to drag me down into mediocrity, a hellspawn trying to send me back to a soulless life in a cubicle farm. And that wakes me up, gets my blood pumping, to get back to work. I *will* maintain my schedule and my practices and be productive when productivity is *demanded*, because I would rather quit technology completely and work on a farm than go back to a cubicle farm.

If you can get your team together in the same place once a week for--say--3 hours, do it and work together. Coworking is incredibly motivating and a LOT of fun. It's hard to sit on the internet and cruise the Lounge all day when you have your friends sitting with you all working. And physical contact with other people is an incredibly powerful tool for motivating and invigorating people onto the mission.

Whatever you do, make it routine. Put it on the calendar. Cherish that time. Don't abuse it. Don't work when you're not supposed to work; that makes it too easy to not work when you are supposed to. Force yourself into the routine.

Awesome. Glad it's working out for you. If you haven't already, check out www.lifehacker.com, there are a lot of great articles on this sort of stuff.