As far as non BTC/ LTC/ NMC coins..
Yacoin - Not a lot of network hash rate (100Mhash, June 13th) but the most interesting internals of any coin. This is also currently the only alt coin where I actually bought some.
Digitalcoin - Good adaption. Possibly the best network hash rate (~1Ghash June 12th) from any recent alt coin and exchange rates are fairly good.
Both of these have very good chances at being the coin to "make it" IMO.