Most Bitcoin lookalikes are not really worth looking at. The two that are more or less accepted are Litecoin and Namecoin, of which the latter is not intended as a currency. Another more or less popular cryptocurrency that is not based on Bitcoin is Ripple.
I know that there are many more Bitcoin-based currencies. Most of them are not adopted and are thus insignificant. The value of such currencies is made by the willingness of people to exchange them for value, like objects or other money. As long as no one uses these alternative currencies, they are of no meaning at all.
And frankly, wouldn't it be better to first try to make one cryptocurrency succeed instead of spawning hundreds of others before the world knows what a cryptocurrency is?...