Well there are coins that have inovations in security and speed for better transactions and other that might have that but also do something else besides being a currency. There are also others that were "premined" or "defacto premined" this means that there was not a real effort to tell people that the coin exsits, then suddenly it appears but lets say one million were mined already with little effort "scamcoins".
I will just make a short list of some of the more interesting ones:
Namecoin NMC- bitcoin clone but the network allows the creation and management of .bit domains, these are not under ICANN so no censorship, you also need software to view .bit domains.
Peercoin PPC- uses "POW" proof of work as a way to tell whoand how much was mined, hey I havent had time to really fully grasp the whole POW thing, but it is somehow cool heavy math.
Primecoin- Different algo as litecoin and bitcoin, only CPU mining (so far). also uses "POW" and mining does something "usefull" it creates really really long prime numbers. On the one had that -could- be useful, on the other hand atm there is no clear use. So a mix of currency and primenumber generation. Faster transactions than bitcoin (litecoin is also faster)
Quark- only CPU mining, werid changing algo, secure, funny name, atm kind of hyped. Problem was a debated defacto premine.
Securecoin- simmilar to Quark, main feature is security , lesser known
Also check Annoncoin,Digitalcoin,Fastcoin(im still not 100% about this one but cool concept)
Avoid due to scammy developers, premine ect: Novacoin,Terracoin, Luckycoin,Solidcoin,Goldcoin (sorry Microguy) and many more.
With security the features include ways to stop a so called "51% attack" , preventing "double spends" and/or making the transactions more annon.
