Really?
Namecoin is interesting, and has potential.
Datacoin, also has potential, but is only just starting out, so I wouldn't put more than 20-40 dollars into it.
Protoshares haven't even started out yet, they're just hype for a currency which won't come out for at least half a year, if ever. I've held on to about 5 percent of those I mined at the beginning because the concept could do well, but I wouldn't invest anymore until they actually put something of use out.
Mastercoin, sadly enough, appears to be doomed. They're main selling point was that they were like colored coins, but had a huge fund to expedite development. It appears that the people running it are absolute morons, as they're first real developer isn't even going to start until February, and the creator owns something like a quarter of all coins.( They claim this was fair as he sent in a couple hundred Bitcoins for these mastercoins, into a pool he controlled- where everyone else's risk was that he was a scammer.)
If I had to choose the best four current alts,
Namecoin would be there as something with potential, but unlikely to gain too high a value(as that could actually hurt it's usefulness).
Datacoin would be worth investing into, but far too risky at this point for any significant funds. Haven't seen what will happen when someone uploads cp for instance...
Peercoin, as one of the most innovative coins. Money supply increased in such a way that no holder's holdings actually decrease as a percentage of the whole(i.e. Money supply increased via interest on everyone's holdings.), environmentally friendly, much lower risk of 51....
Anoncoin - They're implementing zerocoin. I'd put in about 2-5 percent, just to see how they fare.
I'd probably add litecoin as well, not for any benefits it provides, which it doesn't really, but because of brand recognition.
Zerocoin will be released as a new coin so I would wait until it comes out to invest in that rather than Anoncoin.