Litecoin, namecoin, peercoin and primecoin look the most promising. The jury's out on the likes of solidcoin, worldcoin and a few others.
The only reason those coins are on the radar is because you can trade them for fiat.
That's fine if you're impatient and want to sell a coin for a fraction of its future worth.
My guess is that the big ones will be cryptogenic bullions, anoncoin and/or megacoin.
Cryptogenic bullions will be the first one with virtually no inflation.
Anoncoin ihas an i2p niche.
Megacoin might beat anoncoin at the zerocoin race.
I doubt they'll be worth what bitcoin's worth though.
