Well, as you may know, I offer webspace for everything homebrew related.
Last year, Sousanator wanted to create a site dedicated to SmashGP / SmashGPSP.
I just wanted to post about it here, as it has grown quite fast, you can now find over 100 characters and over 30 levels (though not all levels work with the GP32-version) already!
So, if you want to play SmashGP and are longing for new characters, you should take a look there!