SuperTux is loosely based on Mario and there are tons of scrollers out there, so I don't think it's worth to add it. SuperTuxKart is similar in that it doesn't even mention Mario Kart anywhere, which I take for being a bit more separate/independent from franchise than most games in this list are.
SuperTux – http://supertux.lethargik.org/ – a Super Mario Bros. clone. It actually has a lot of original level ideas.
SuperTuxKart – http://supertuxkart.sourceforge.net/ – a Mario Kart clone, though with more simplistic kart physics.