This is for open wrt - but it is nice that it gives you specs on the boxes. http://wiki.openwrt.org/TableOfHardware If it is supported on open, it may eventually covered here.
Rule of thumb is it has to have 2mb flash space - 4 preferred.
I think you are likely referring to the RG1000. I have one of these still myself. They were available rebranded by HP (as mine is) and others, and there were later model variants as well. Basically these are equivalent to the original Apple Airport models, and can in fact run certain Apple firmwares using specific flash loaders.
It is supposedly possible to run x86 Linux on it, but it requires loading the firmware over an NFS network at every reboot due to the limited onboard flash (512k). I've never tried it myself.
There is/was proprietary firmware for sale (Karlnet) which allows these to run in a point-to-point bridge mode, and maybe allows other function, but I never tried it.
Last thing I did with mine before putting it into mothballs was to flash it with the AP-500 (or was it AP-1000?) firmware, which allows for more setup options, such as Radius authentication to go with the WEP, SPI firewall, etc.
If you haven't seen it already, there is lots of info here: http://www.seattlewireless.net/OrinocoRg1000
as well as other sites you can find with a google search, though many of the links are becoming very stale now.
It was a decent little unit hardware wise for the time, cursed with miserable firmware out of the box. With the AP firmware it still makes for a viable "b" access point, unless you need WPA type security etc. This is partly why I held onto mine, in case I ever needed it.
i have read tha it can be a wireless client bridge by itself with any firmware flashes. but i have yet to be able to get the setup to work.. it is a very confusing set of instructions
Are we talking about the same unit? Is it this: http://www.murgatroid.com/rg1000/rg1000.htm ?
If it is, and if you are saying the stock firmware will do client bridge I'm sure you are mistaken, and I'm fairly certain that I've discussed all of the available options above. With only 512kb of flash to hold firmware, the options are limited. Of course if you know something concrete that I don't, I'd be happy to hear about it! Prove me wrong (please)! What "instructions" are you trying to use? Maybe you are confusing the terms "residential gateway" with "client-bridge"?
It looks like you are confusing "BSS mode (also known as infrastructure mode) bridging". All that means is that it will bridge between wired and wireless connection. It does NOT mean that it will operate in client mode. So, you can use your dd-wrt flashed FON as a client to bridge a device tthrough the RG1000 access point. You can not run the RG1000 as a client. Sorry to burst your bubble!
What "instructions" are you trying to use? Maybe you are confusing the terms "residential gateway" with "client-bridge"?