I'm interested in mining and would like to know if there are any consumer grade computers available that can mine any of the alternative coins. If so, what computers and which coins do you think would work fairly well?
Simply put all consumer grade computers "could" mine bitcoin and other altcoins, the question you're probably interested in is regarding profitabiltiy.
At this point in time people are still mining scrypt based altcoins with specially built machines with multiple high performance GPU's. Whether this is profitable depends on your circumstances for example power price per kW/h, the price of the coins you're mining and the cost of the rig you build/buy.