I used the Edimax 7811Un successfully in the RPi`s own USB port. Making use of Debian Squeeze I had no problems using a script the OP provided in that link in the post above mine. The problem started when I updated the firmware in debian Squeeze and the adapter failed to work with the OS from that point on.
Work went on to rectify the matter but I`d been trying the Debian Wheezy Alpha distro and was so impressed by the increased speed and feeling of being rock solid that I wished to continue with it. The Edimax did not work in that, but the same link above describes a new patch that came out very very quickly after the beta of Wheezy was released. I am using both and it works perfectly well, again still in the RPi USB port with no powered USB Hub in use. My MS USB keyboard/mouse adapter is plugged directly into the remaining port.
This Edimax adapter is fast and small. It's readily adapted to changes of distro, albeit by a provided script and subject to goodwill. For me it was a bargain and only £8.95 inc free delivery. Well worth taking the chance on it.
http://www.raspberrypi.org/phpBB3/viewt ... &start=175
Page 8, well down the page. Download the script ready for getting the Pi. When you do there`s more than one way to do this but here goes. Setup Filezilla or similar windows FTP to connect to your RPi IP. Using ifconfig (not ipconfig) should tell you it, but look closely when it boots and you should see it, I set mine to static instead of DHCP addressing so I know what the IP is every time it boots-the router has the Pi Mac address set to the same IP too. Upload the script to the RPi then log out of Filezilla. Log into the RPi as SU root, type in startx for the GUI Desktop, look in OTHER for file manager and move the script to /BOOT. The link has a way to do this with a command instead of using Filezilla, so there are two choices so far.
Use the given command on the above link to install the Edimax and drivers. Put in the Edimax adapter only when told to do so and reboot. It was after this process and a few tests that I added STATIC IP addressing on both the wired and the WiFi connection. Good luck and enjoy,