Some real truth here, not like the shills promoting their coin in this forum. I have a little bit of each of these but I would strongly recommend being very very conservative with your altcoin bets. I don't allow alt-coins to exceed 12% of my total position.
LTC, NMC, and PPC - these are first generation alts and have been around for a while. Of these I like NMC the most, I could really see it exploding in five years or so. People these days don't understand Namecoin... its simplicity is its strength. There's a reason why Atlas (wall st.-backed exchange) is implementing support for only Litecoin and Namecoin (outside of Bitcoin).
VTC - adaptive-N scrypt seems like a good longterm bet.
DOGE - for its community which will probably never stop using it. It's got a black market backing its value as well (dogeroad)
NXT - the first PoS coin, lots of development
NEM - seems like a lot of thought going into this coin
HUC - a solid human-mineable coin.
Currently I am looking to buy in cheap for AUR (maybe a couple months after this airdrop plays out), DRK (good dev, lots of real innovation, low inflation), HIC (X11 algo seems like a smart bet, this is more of a short term play as the market cap for this coin is still small so the upside could be huge).
Remember, any and all of these alts could go to 1 satoshi. When you invest and hold an alt, you need to be prepared to lose it all.
(Emphasis mine.)
I agree about Namecoin and Huntercoin. They are not well understood by many people, and the underlying technology there, while still experimental (as are all cryptocurrencies), has many deep and far reaching implications for "real-world" applications.
NMC and HUC have immediate and clear uses beyond being currencies. They have much more going for them than your typical clones/variations. When people begin to understand the technologies better, they will shine much brighter than they do now.
Both NMC and HUC have active development as well.