Gnomon

Tom: first of all, Nintendo *has* come out with an official media player. It's called the Play Yan. (If by asking for a "decent" player you were deliberately excluding this device, please grant your pardon and ignore the following bit) It's even available in namerica now. The thing has some ingenious bits - it even includes its own headphone jack to bypass the dongle annoyance and relatively low quality of the GBA SP output - but the interface is awful and it's a non-starter. The hobbyist scene is more likely to produce nifty stuff anyhow. Check out Moonshell.

Second of all, there are most certainly flush MiniSD and MicroSD hobbyist carts for the DS and the DS Lite now, yes. Check out the Supercard Micro, the M3 Perfect or the M3 Lite: these all allow one to boot DS and GBA homebrew code with the appropriate PassMe device; the M3 Lite even sits flush inside the GBA port on a DS Lite. There are other options as well - the DS-X and the M3 Simply come to mind - which are boot and code-holding devices in one, but they both suffer the drawback of not being able to run GBA games natively on your DS and not having the additional 32 megs of DSLinux-pleasing RAM that the earlier devices contain. Your very best bet is two 2-gig MicroSD cards, an M3 Lite and an M3 Simply; you'll be loaded for bear.

TheMayor, Dan Russell: your comments disappoint me - not because I disagree with you, but because you may be right. The term "hacker" only recently acquired primarily negative connotations. It has traditionally been a term both complimentary and respectful.