From the list the TC posted:
Clubhouse Games
Tetris DS
Video Games Hero
Magnetica
New York Times Crosswords
I either haven't tried or don't care for the others listed.
For those suggesting games, could we get short descriptions? I know I can "JFGI" but it's hard to get reliable information from one source (my first stop is actually Wikipedia).
From my microSD card:
Puzzlemaniak (Homebrew - you can get it here on GBATemp - lots of minigames)
Luxor: Pharoah's Challenge (Zuma clone - shoot colored balls at a chain of balls to get a group of 3 or more)
Powder 1.07 (also Homebrew, also here. Another Hack/NetHack clone. Looks promising, looks better designed for the NDS than NetHackDS)
Setsuzoku no Puzzle (another homebrew - it's a tile-matching puzzle game. Japanese name but the game is translated to English).
Not too many