Is there a way to tell which *coin is most profitable to mine? Basically a program that could run some hashes for all of the different hash functions that are used in the different big cryptocurrencies and then get the current difficulty from all of them. From there you can determine how many of those coins you could be mining and look up an exchange rate from there.

I was guessing that I should switch my GPU mining from bitcoins to litecoins, but I was just wondering if its worth it.

I was thinking about starting to write a small script to do this automatically if nothing like it exists.
This site allows you to compare the mining profitability of the various coins: 
http://dustcoin.com/mining