There are cpu-mining only altcoins like primecoin, protoshares, quarkcoin. I have mined all of these on our university clusters for a while (and got busted
). Primecoin has too high difficulty now ... Protoshares has some future probabbly. I personally dont like quark. I dont know which of these 2 is more profitable now.
Than you can also try mine scrypt coins on some multipool (it automatically mines most profitable coin and trades it to btc) like middlecoin.com or hashco.ws