I wanted to play around with some altcoins but many of the main websites are sketch at best. For example when checking out UltraCoin, their recommended miner has spyware in it. What altcoins can you trust?
never download any file from any of unknown or new altcoins that just came out, unless you know programming and can check the code yourself.
if you want to invest or have an altcoin's wallet you can always make an address on an exchanger, although it is not recommended to keep money on an exchanger, but it is safer to download an unknown altcoin's wallet.
another way is to make a virtual machine on you computer, with a program like virtualbox. this way you can protect your system from any malware. you still have to be careful though.
also you can mostly trust altcoins that are old and have a huge number of users, that way you have lower chance of getting malwares.