When you install Snow Leopard (as I did yesterday) you may find that some of your hw will not work even if you can install the drivers. I also have a MBP 17" that did the same with some 3rd party drivers (like the one for xbox 360 controllers / they still can't work... that's another story).
The problem is when Chameleon (I have installed it using the tuto depicted here) launches SL, it does in 64mode by default. When you launch the OS in this way, it start the 64bit kernel that needs 64bit drivers... and the ralink drivers, ntfs support(paragon/macfuse) and others are in 32bits so they can't be loaded.
The fix: launch Snow Leopard with the 32bit kernel(other programs keeps running in 64bit)
- Start terminal
- Type sudo -s and type your password. CAUTION: you're right now in superuser mode... so be very careful...
- locate the folder Extras in "/"
- edit the file com.apple.Boot.plist (using nano)
- locate the KEY "Kernel Flags"
- insert this value: "<string>arch=i386</string>" (you may find here an empty <string>... you can use it...)
- Save & close the file (in nano is Ctrl-X, confirm the name and press Y to acept all changes)
- Install the Ralink driver (or other 32bit driver you need)
Well... I hope this can help you... remember, this can help with a lot of 32bit kexts, but you cand find some others that maybe don't work for you... and sorry for my bad english.