This thread turned into a good overview of carts, nice! I would've loved to see more 'playable' software on carts!
guess what - in the "saturn copy protection" thread on SegaXtreme, somebody mentioned the Mahjong cart again, saying it was included on a cheat cartridge (which kinda makes sense). What I'd like to see is somebody who is more crafty with electronics to solder some more address lines from the connector to the ROM, and thus making a Saturn flash cartridge (H)
I think the mini-CD approach has already been tried but doesn't work due to alignment issues - unless you laser a hole in the Saturn disc with surgical precision, and make it a stable fit.