It looks like a clone of hundreds of similar sites that have popped up over the past year. I think you could use a more creative logo.
It is clean and the layout is nice. I think it is going to be tough to compete with the likes of facebook which already has groups coded into it. What would your site offer that facebook can't?
nice its clean and simple. but at first look without scrolling, I think its a blog site. o_O can use community pictures though. Another thing is, try to validate your css. I think you have a couple of errors.