Since we don't have any computer programmers in our co-op, I just started up a free page on shutterfly. They have some nice options on format and ours is set up like a sports club. We have a spot for photos, journal, calendar of events, message board, etc. It's worked out very well and we have pretty good participation of posting trail cam pics and harvest pics. In just over a year we have almost 6,000 hits, pretty good for a little hunting group!
I agree on the people management. Not everyone will want to post pics, be involved, or agree with what you are trying to do, but ever so slowly more and more will come around and after a few years you'd be surprised how large the co-op will be.
Stay positive!! That's the biggest goal you should have as a leader, make it fun and make people WANT to be involved and think it's cool and a fun thing to be part of. Check out my website if you want ideas: www.weasaldamdeerhunters.shutterfly.com