Q:

List of Bitcoin forks or spinoffs

I've just heard about another digital currency called Litecoin, which I believe to be based on Bitcoin, are there any more alternatives to Bitcoin & Litecoin?

Any one got a list?
A reason why the alternatives are better and/or worse?
With what intentions where they created.

A:

Forum user xorxor maintains a list:

http://bitcointalk.org/index.php?topic=134179.0

A reason why the alternatives are better and/or worse?

The secret sauce for Bitcoin is how the proof of work approach allowed it to be a decentralized digital currency.  This approach allows "truth" to be determined by consensus of the network.  This also makes it vulnerable should the majority of the network not be honest. 
Keep that in mind first and foremost when considering any alternatives.

