I took a chance on the cheapest micro wireless dongle I could find on ebay (£4.50) (3/2/13 - Just got one of these for £3.89, and can confirm it works fine - seems to be the same as the one I originally used. - The original supplier on Ebay put price up to something stupid! http://www.ebay.co.uk/itm/310574944823) - It worked very well in windows, but I really wanted it for the Pi. It was relatively straightforward to setup. Obviously you need a working connection of some sort to download the required files. - I did this by bridging my wireless connection on windows7 with the (otherwise unused) wired connection and plugging the Pi.
1. - The package firmware-ralink from the Debian Squeeze install doesn't work - it doesn't contain the right firmware.
2. - edit /etc/sources - add in wheezy as a source instead of squeeze.
deb http://ftp.uk.debian.org/debian/ wheezy main non-free
###deb http://www.debian-multimedia.org squeeze main non-free
3. - sudo apt-get update
4. - sudo apt-get install firmware-ralink
5. - Before you forget, reverse the comments in sources.list so that you put it back to squeeze and run apt-get update for good measure.
6. - Plug in the wireless dongle.
7. - Should be able to see it in lsusb:-
Bus 001 Device 004: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter
8. - edit /etc/network/interfaces
iface wlan0 inet dhcp
9. - sudo ifup wlan0
If all has worked, we should now be assigned a wireless IP address, and can unplug the ethernet. - Reboot to test.
10. - I then wanted a static IP for this. - This is simply configured in interfaces:-
iface wlan0 inet static
Note that I'm using WEP here (because some legacy kit doesn't support WPA) - might be slightly different for WPA.