Cruising around REI's website and found the Big Agnes sleeping mat was on sale. I highly recommend it. It folds up small, light and after you sleep on it, you'll want to throw away that old 1/2 thick pad you've used for years. Here's a couple of links.
www.rei.com/outlet/product/785354 - This is the one I have. I use it for my backpacking also.
www.rei.com/outlet/product/785352 - If your just going to use it off the bike, I recommend this one.
I like the Big Anges because they seem to be able to take some abuse. I have the 4 foot version also when I go caving. No issues with any of them.