I'm a Mortgage Broker, so maybe I can shed some light on this. As has been stated, the type of loan you choose should be decided by what you intend to do with your home. An ARM (Ajustable Rate Mortgage) can come in various flavors (2/28,3/1,5/1 and so forth) but it is a fairly specific type of loan program. It is usually best reserved for people who are either in extreme debt and need the smallest monthly payment possible or are people who intend to move within a fairly short time period. ARM loan adjust after their fixed term expires, by utilizing LIBOR (London Inter-Banking Overnight Rate).
If your simply looking for a low rate, then I would suggest either a 10,15, or 20 year fixed rate. I mean par right now on a 15 year fixed is about 4.45, and a 30 year is about 4.9. Whether or not you want to wait to see if the Fed's lower the rate a little further, or go ahead and Refi now is up to you. Kinda like Vegas. If I was you I would definately get a Fixed rate if you intend to stay in your home.
Word is, that the Fed's may lower rates a little further.
Hope that helps.