ideas for more compact as well as more self-explaining UI designs ..

[koo5]

or just have the front page have just a listing of titles and descriptions and maybe the progress bar?
the progress bar could be made to take up less height:
(The original design should probably be retained for introductory purposes.)
The "We want 50 people:" could be indicated by a "50" to the right.
add tooltips.
add "Participate" button could be next to it?
That's all, the rest would only be on the details page