I didn't try it yet, but I think CLISP should work out of the box on x86 scratchbox (it's just Linux on x86, after all) and then it should be possible to use it to build SBCL.
Well, if you want a relatively easy to install CLISP package, you'll have to wait a few days until I make it, sorry, too busy right now I'll need to publish it along with all my latest patches so that I don't violate GPL in any way. As I've already mentioned, here is the patch for clisp-2.48, but building it from sources is rather tedious.
I don't know, didn't try yet. There was an effort to make ECL work on iPhone and seems like some of the problems were ARM-related, so I'm not 100% sure there will be no problems with ECL on Maemo. Also I suspect that you'll have gcc on the device to be able to compile lisp code with ECL.