Amazon B2G1 free on select games.Pretty good selection. Included are:
3DS: OOT 3DS, Resident Evil: The Mercenaries, Pilotwings Resort, Ghost Recon SW, Steel Diver, etc.
DS: Okamiden, Ghost Trick, Monster Tale, Chrono Trigger, New Super Mario Bros., Layton Unwound Future, Super Scribblenauts, The World Ends With You, Zelda Phantom Hourglass, etc.
Wii: Wii Play Motion, Super Mario Galaxy 2, Disney Epic Mickey, Monster Hunter Tri, Metroid Other M, Sin & Punishment 2, Conduit 2, etc.
And of course tons of PS3, Xbox 360, PC, PSP, etc. games.