There's a couple popular sites that do it, middlecoincom, [Suspicious link removed], multipool.us.  I've been using middlecoin and been happy with the results (they auto exchange and pay out in BTC).  https://bitcointalk.org/index.php?topic=259649.0  Hashcows was recently hacked and are still in the process of rebuilding.  Multipool does the switching, but you'll need to exchange the coins yourself.