okr on 01 March 2010
Nothing against VGC's DS recommendation thread posted in the first reply, but the following thread is sensational, way more up to date and mentions not only the most popular/obvious ones but also many great, overlooked DS games which are rarely mentioned on VGC (such as Dawn of Discovery/Anno 1701, Soul Bubbles, Broken Sword: Shadow of the Templars and others) as well as plenty of upcoming games: http://www.neogaf.com/forum/showthread.php?t=222049 (best recommendation thread I ever saw; but be aware - depending on your connection it may take some minutes to fully load).
Essay Pro