We've done two logo contests at 99designs (formerly SitePoint Contests), and we loved the results of both. We made sure our prize was the highest on the site for a logo at the time ($500 in each case), and so we got tons of entries, quite a few of them very good. We even got a goatse entry: http://inthebox.webmin.com/its-just-not-a-contest-until-you-...

This is by far the best one: http://99designs.com/contests/6774/entries/442807.png

agreed, but im a sucker for avenir

i wouldve made a graphic depicting two old farts yawning

Umm... FAIL: "Stock Overflow" http://99designs.com/contests/6774/designers/245246#entry-44...

One other thing -- I notice all the stacks are overflowing from the top. Shouldn't they be overflowing from the bottom?

Depends on machine architecture.

oh god.. I'm not sure what to say about this entry http://99designs.com/contests/6774/designers/245401#entry-44...

duh... isn't that obvious http://99designs.com/contests/6774/entries/441391.png