I am compiling a list of all the exchanges that exchange at least a few alt coins.
Please feel free to add to this list. And I will update it.
cryptsy.com(lots and lots of coins)
https://www.crypto-trade.com/ (BTC, LTC, NMC, XPM, PPC, TRC, FTC, DVC, WDC, DGC)
https://bter.com (MANY coins, apparently some people have problems withdrawing their coins atm)
https://www.coins-e.com/ (MANY coins)
https://vircurex.com/ (ANC, BTC, DGC, DVC, FRC, FTC, I0C, IXC, LTC, NMC, NVC, PPC, TRC, WDC, XPM)
https://www.therocktrading.com/ (BTC, LTC, XRP)
https://cryptonit.net/ (BTC, LTC, FTC, PPC, TRC, NMC)
https://www.kraken.com/ (BTC, LTC, NMC, XRP, XVN)
btc-e.com
