having personally a good deal of experience in the "alt" trading world , my best advice is that most of the "alts" (anything that's not btc) live fast and die hard in terms of price.
most are created with the express intent of pumping and dumping these coins on willing participant exchanges - you can sign up for one such market (cryptsy) in my signature - there you can find literally hundreds of "alts" to convert your btc into.
other "trusted" options for alt exchanges include poloniex and bittrex.
if you plan on buying and holding , do not hold the coins on any of these exchanges that allow you to trade alts - they could disappear tomorrow.
also - if you're looking at obscure coins , try to at least find ones which are traded on more than 1 of these exchanges - coins on these exchanges are delisted and the exchanges themselves have been known to shutdown so it's a good thing if you can re-sell your alt-coins on more than 1 exchange.
litecoin and darkcoin are considered relatively decent frontrunners of the alt-coin world.
other relative oldies include namecoin and peercoin.
some of the alts cost only hundreds of satoshis (the smallest denomination of btc 0.00000001) - some can actually be obtained in the single digit satoshi land - these are almost universally considered junk , but as with all of the alt-coins , the possibility of using btc to pump the price up and then sell for profit exists.
if you're not doing the pumping of the price , or getting in on a coin the day it's listed , it will be near impossible to make anything on your purchases.
it is fun owning 1,000,000 of something when it costs you 50cents , even if it is total crap.
also each and every one of the alts has their own announcement thread if you look for it , and you may be able to gather some information regarding the current level of ongoing development / commitment to said alt , which is a good way to attempt to sort the shit from the crap.
goodluck
