My pick are LTC, PPC, FTC and XPM maybe.
Lite coin is most popular after BTC, following with the PPcoin and prime coin.
Currently i invest buy/sell to feather coin.
I never really got feathercoin. I like XPM, PPC definitely has it's place, curecoin is useful at least and I like quarkcoin as an actual currency, not for hoarding due to it's speed.