I thought only Acekard RPG had built-in memory (NAND I believe)...
For homebrew, I can recommend some that I find addicting/useful.
-DSOrganize 3.1129 (helpful for most of the other cards because it can copy/paste/delete, though the Acekard can do that by itself anyways...but it can also rename files, change wifi settings, semi-browse the internet, among various other organizer sort of things).
-Moonshell2 (Mostly if you just want to have media stuff in a really smexy GUI. ie: images, music, videos, text)
-Comicbook DS (Just like the name implies, you can view converted packs of images on your DS, and its probably compressed somehow, unlike when viewing with Moonshell2, though as an alternative, there is also Image Viewer by the same person that made Moonshell2).
-Animanatee (Nifty animator that animates your drawings. Think flipbook)
-Colors! (Great and simple painting app)
-Phidias (A professional-ish sort of painting app with quite a few options and things, I've never compared UAPaint with Phidias before though)
-UAPaint (This has more options than Colors! and is probably better for things that aren't freehand.)
-VNDS (so I'm advertising this a bit because I like it, but its kind of dying because a spammer or two got a hold on the messageboard and posts NSFW images, but anyways it is a visual novel reader that can view visual novels specifically ported to the VNDS...kinda limited though)
-SNEmulDS (SNES emulator that is probably the best at the moment, and as a really amusing game there is "EVO Search for Eden")
-NeoDS (NeoGeo emulator for those fun arcade games like the King of Fighter series, Metal Slug, and some other things)
-Pocket Physics (A fun physics sort of emulator, there is also Rubberbands which is a little less complete, but its still kind of fun to play)
Games: (I'm just going to list them since its kind of long)
-100 Boxes Puzzle
-Anime Jo All Star Kirifuda Taisen DS
-ChatNoir (simple idea, but I can't win easily xD)
-CrackAttack (or TetattDS. I would say TetattDS looks and feels more professionally done)
-AcChen (or Setsuzoku no Puzzle, since both are similar gameplay)
-GeoWars (haven't tried it, but it looks good)
-Knytt Stories DS
-Plants vs Zombies
-Puzzle Maniak (haven't tried it, but it looks good)
-Ripholes in Rubbish
-Shooting Watch DS
-Take the eggs! Ornithorhynchus Anatinus GO GO GO! DS
-Touhou DS (weeaboo.nl)
-Whee! DS (second version)
Lol, I've never had any problems with it either, but prudence is always good when referring others (I think). I wouldn't want them to come back telling me that DSO 3.2 screwed up everything and that I should have recommended the one that is supposed to be the most stable.