I haven't looked exhaustively.
After the chargify free account fiasco, I'm staying away from them. I would have started with the free account there and moved up, but now I'd be too nervous to look at them. Not familiar with the others, but I'd be nervous to go with anyone who doesn't have serious momentum, or size in their favor, as I don't want to rewrite my code if a startup fails or deal with stranded account information.