Hey guys, I just ported a tiny game to Dreamcast. It's called SDLLopanDC and it's a Mahjong-like game. It was originally developed by Dave Ashley (http://www.linuxmotors.com/sdllopan/ )
It works both on nullDC and a real Dreamcast. As Neoblast made me aware of it, it was already ported to DC in 2006 by ron. However, the original game has seen an update since then, so this can be considered "a better port".
Controls
Digipad: control the cursor
X / Y: Select a tile
L / R: create a new playing field, reset the game