I've been playing on ZeroRiskPoker.com for the past couple of weeks. It's actually pretty cool.
Basically, it's a free site where you play for prizes. It's sponsor-based and there's stuff like magazine subscriptions, poker chips and even WSOP seats available to be won. Since that player never pays a thing, it isn't gambling and therefore not 'questionable'.
Only thing is it's not for Mac right now - I've been playing via parallels - so it isn't an option if you don't run Windows. But if you do, and you're a poker fan, check it out. It's a pretty cool concept and I already won a few prizes.