Depends on your DS, really.
Game carts (slot 2):
I use the incredibly inexpensive GBAMP, which works fine for just about everything.
ROMs exceeding 4MB, such as HexenDS can't run, but more and more developers are actually storing game data on the filesystem on CF/SD cards instead of within their ROMs. As a result, it should have a long life ahead of it, assuming that people don't start switching to writing software that runs off boring game cards. Heck, even MiniVMac works on here!
The maker of the hacked GBAMP firmware has reportedly ( video and everything :( ) created a firmware for it that has XIP support, enabling it to run roms of any size by streaming them as with a conventional game cart, but he refuses to release it since it would also help the software pirates. (And I, for one, actually prefer when ROMs stream from a seperate data file on the DS).
If you feel like something a bit more fancy, Supercard SD almost fits into the GBA slot, and Supercard CF sticks out a bit more (well, the CF card sticks out). Both Supercards have 32 MB of RAM built in along with XIP support.
The M3 (sequel to GBAMP) is another quite fancy cart, with some nice features and, like the Supercard, a strong link to piracy. (*sigh*).
Afaik, people have trouble with homebrew on the M3 and it isn't hugely popular, but the Supercard is pretty good for stuff like DSLinux. The Supercard build of DSLinux has over 1 MB of RAM more than the GBAMP build, which allows it to run nano-X and crash far less while using the web browser.
Passthrough devices:
With an older DS that only needs PassMe1, PassMe1 followed by flashing the firmware works nicely.
With a DSLite or a DS needing PassMe2, I would recommend using a "No-Pass" device like the Datel Max Media Launcher.
Costs a bit more but it works! (And, since flashing the firmware on a DS-Lite is risky, there's less temptation to do so since it doesn't stick out of the slot).
And, actually, even with a PassMe1-needing DS, a nopass device is great :)
Game carts (slot 2):
I use the incredibly inexpensive GBAMP, which works fine for just about everything.
ROMs exceeding 4MB, such as HexenDS can't run, but more and more developers are actually storing game data on the filesystem on CF/SD cards instead of within their ROMs. As a result, it should have a long life ahead of it, assuming that people don't start switching to writing software that runs off boring game cards. Heck, even MiniVMac works on here!
The maker of the hacked GBAMP firmware has reportedly ( video and everything :( ) created a firmware for it that has XIP support, enabling it to run roms of any size by streaming them as with a conventional game cart, but he refuses to release it since it would also help the software pirates. (And I, for one, actually prefer when ROMs stream from a seperate data file on the DS).
If you feel like something a bit more fancy, Supercard SD almost fits into the GBA slot, and Supercard CF sticks out a bit more (well, the CF card sticks out). Both Supercards have 32 MB of RAM built in along with XIP support.
The M3 (sequel to GBAMP) is another quite fancy cart, with some nice features and, like the Supercard, a strong link to piracy. (*sigh*).
Afaik, people have trouble with homebrew on the M3 and it isn't hugely popular, but the Supercard is pretty good for stuff like DSLinux. The Supercard build of DSLinux has over 1 MB of RAM more than the GBAMP build, which allows it to run nano-X and crash far less while using the web browser.
Passthrough devices:
With an older DS that only needs PassMe1, PassMe1 followed by flashing the firmware works nicely.
With a DSLite or a DS needing PassMe2, I would recommend using a "No-Pass" device like the Datel Max Media Launcher.
Costs a bit more but it works! (And, since flashing the firmware on a DS-Lite is risky, there's less temptation to do so since it doesn't stick out of the slot).
And, actually, even with a PassMe1-needing DS, a nopass device is great :)