Does anybody have a list? I don't want to invest in any scams.
So you've already seen a long list from other users, which you'll have to digest on your own due to your research. What I'll add is that you want to look at what coins are being actively developed and not just rotting...when considering Altcoins, look to what they offer Above what bitcoin offers, if they are not innovative (read: if they are a clone) then they have a LOT of catching up to do with bitcoin which has first mover advantage. Most clones are pump and dumps, plain and simple, users are hoping to make money by driving the price up and cashing out...these coins will likely have a short life span and long term holders will get burned.
Something has to offer value above that which bitcoin offers in order to get people to actually use it. Just look at your regular life, its hard for makers of new pad devices to get users unless they offer sufficient incentive to the ipad....lower price, added features, etc... The same can be said of any product. People dislike change immensely and won't change unless there is a significant amount of value added. Now, with superior marketing a coin may in time prove worthy competition to Bitcoin of course, it is a market after all, but you're then basing your decision upon the marketing strategies of various holders and investors, etc...
In short if its the same as bitcoin or a clone of another altcoin then its likely not a good investment period as those coins are operating at a comparative disadvantage (they lack first mover advantage). If they offer something different then you have to wonder to yourself what people will be wanting a few years from today, if you think a coin offers that, then its a good investment in your mind. Its hard to predict human behavior, of course, but this is what investors seek to do daily.
Good luck.
For me I'm only interested in PPC and Bitcoin...I don't think litecoin offers enough of a difference to Bitcoin but I may very well be wrong and people really want it to succeed because of their holdings...there is something to be said for that. People have criticisms of PPC as well, and they are not necessarily invalid, its all about what you see as being useful and adding value. I also am watching closely the development of Netcoin.
Ofc this is just my opinion, and as you've seen here if you ask 10 different people, you'll get 10 different answers.