decided to finally connect my ds to the wifi, how do I setup AOSS? I use WPA2 and the DS (even lite and dsi) don't support WPA at all.
so I was curious, how might I setup AOSS or a dual network with my copy of DDWRT on my WRT54g?
I can't seem to find any walkthroughs.

Firstly, congratulations on the most unintuitive and acronym laden post I've ever seen, its a masterpiece.
I don't think the one touch setup buttons work right under ddwrt, at least they sure as hell didn't when I tried it, manual is better anyway since you know what changes you'lol be making.
So you want to have the DS which doesn't support WPA2 connected to a WPA2 enabled network? Assuming it supports 802.11g, you should be able to set the wireless security mode to WPA2 Personal Mixed (in the Wireless / Wireless Securty tabs).
That mode will basically poll each device on connection, discover its maximum level of security and provide it accordingly. That would let you use full WPA2 encryption for laptops or any other device that supports it but also let it step down to use WPA1 for older/cheaper NICs like the DS apparently has. Thats the way I connect my PSP to my network and it seems to work quite well, allows the PSP to connect to the network and doesn't compromise the rest of the network's security so I've still got the 3rd best security for a computer (second being cables, first being no network)
If it uses WEP or no security at all, you'd have to set up a virtual interface on the router, that should let you make a bridged connection and use a seperate encryption standard for it (see attached)

The DSi -does- support WPA, however Nintendo in their wisdom decided to allow the carts to carry the wireless drivers for multiplayer, so the actual -game- needs to support WPA to connect. Only a handful do so far.

Err what? They have drivers embedded in the game cartridge rather than in the device? Thats the most retarded design decision I've heard of in years, if it controls the hardware, it should be part of the OS!

According to Wikipedia's Nintendo DSi page it is the only model that supports WPA/2 with the rest (DS and DS lite) being WEP only.
I run a custom strain of the DDWRT codebase for a WRTSL54GS. One of my favorite features
is the ability to remap the "easy security button" to different functionality (i.e. rebooting router, power switch for transmitter, start ftp or sshd, etc.) through scripting. Since security settings aren't repeated frequently I prefer to just handset them and get more mileage out of "the button" by remapping it.

The OS does have its own drivers (the DSi web browser/app store supports WPA), but it's something to do with how the protection system works - the game itself has no access to the OS layer.

Hmm, probably runs in a protected shell so dodgy carts can't get kernel level access. You'd think they'd just have some network layer tunnel to stop with all the fucking about and not make developing harder than it needs to be
Then again it IS nintendo...

perhaps I need to update my copy of ddwrt, but my version is the light version (got the one with half the ram and processor speed sadly), but when I create a virtual network it doesn't allow me to apply any security other than not broadcasting the ssid, and if I choose that my DS can't connect anyway.
I'm going to seriously look into upgrading it.