I recently bought a EZFlash Vplus SDHC TF NDS Lite Flash Cart with 3-in-1 256M GBA+Memory+Rumble+2*Stylus (White) from www.dealextreme.com Hong Kong. (probably available in your country, just google search)
Ive been using these card for about a week now and its a great combo pack. Using NDS games is simple, just drag and drop onto memory card and its good to go. Using the slot 2 card is ok. abit slow but cant be helped as the GBA games are store on the TF memory card and then needs to write to slot 2 by the NDS but once written, the game will stay put untill another game overwrite it. Game Saves are automatic stored onto the TF memory card.
MoonShell is part of the firmware so all the media features are included. EZFlash Vplus uses ezarcode.dat which are Action Replay codes, gbatemp.net have a regular updated file.
This card doesnt have as much features as Supercard DSOne, like Real Time Save, but it does have Soft Reset and the Menu is simple and easy to use.