A friend of mine on another board posted these pics of her beta.
Does anyone know what's wrong with him?
She says he's acting completely normal, eating, pooping, flaring, just generally being a Beta, but he swims kinda funny because of his tumor. She said it was like a bubble under his skin.

You may want to look through the threads a bit..Lucy had a similar problem a few months back with one of her betta's and there's a pretty extensive thread on how she treated her betta. Sadly her betta didn't make it though.

Looks like a tumor. Could be located on the kidney or liver.

If its a tumor, then I don't believe there is any way to help him. Just keep him happy.

Might also try posting this at ultimatebettas.com, some of the people there might also have some ideas.

Here is that thread Kat mentioned, just in case it helps you at all

http://www.kokosgoldfish.invisionzone.com/...topic=48635&hl=

Good luck with him.

Poor little guy.....Is there any redness around the lump at all?What size tank is it kept in and how often does your friend change out water?