If anyone has some time then there are many projects that need to be ported
Most of them use SDL



Open Source Replications

Commander Keen - http://clonekeen.sourceforge.net/
Already ported to GPx2 and I think PSP.

Jazz Jackrabbit - http://treacle.hewwo.com/jazz/oj/download.html
Already ported to PSP, GPx2 and Palm OS!

Duke Nukem 2D Clone - http://scorpioncity.com/djgame.html

Pingus (A Lemmings clone, far from being finished) http://pingus.seul.org/welcome.html

Some of these games MIGHT be portable.
Open Source Games for Windows
http://osswin.sourceforge.net/games.html

Ofcourse there is some project focusing on Flashback but I think it has already been ported to Windows Mobile but someone has to add on-screen buttons to make up for it, like accessing the menu and such.

OK this is the only thread that made it, the others are broken. Can a mod please delete the other threads by the same title as this one?