I am currently holding only BTC, LTC and FRC (but FRC not for long if they don't change their Diff. algo. soon).
All other coins, if I mine them at all, I exchange quickly for BTC/LTC.
For exchanges, I mainly use vircurex and bter.
If you want to change back to fiat you might give bitstamp a look depending on where in the world you are located.
I'm concerned about various exchanges security, given how frequently MtGox gets hacked (I really don't care if they say "IT WAS DDoS!!" until they're blue in the face, I know for a fact their security is absolute ass). I just set up a Vircurex account, which seems to be a decent interface. Does anyone have any sort of feedback on the security of some of these exchanges?
I'm also waiting on a PM response from the owner of my FTC pool, because I'm sitting on about 3+ FTC that haven't paid out yet, and I have my automatic payout threshold set to 1.1 FTC. I also have damn near 5,000 shares that are unpaid so far. I'm using
http://feathercoin.is-a-geek.com if it matters/anyone is curious.