I bought some frogbit and java moss from trinsfish on eBay a little over a week ago. The seller ships from Ohio which is pretty close to me so the plants arrived fast and very healthy. Although it does come with some snails and quite a lot of duckweed, but once I gave it all a good rinsing there wasn't any problem.
As far as surface plants go, I really like my frogbit. It looks like a bunch of lily pads and is actually pretty cute in my tank. Another plus is that although its supposed to be a pretty fast growing plant, it won't get as out of control as duckweed would.