I just finished installing the TL-WN722N TP-Link wiresless USB adapter on a Ubuntu 11.10 machine. I started off with the instructions on http://dwiel.net/blog/tp-link-tl-wn722n-on-ubuntu-10-04 and at least for me the steps were much more simple.

All I needed to do was:

$ wget http://www.orbit-lab.org/kernel/compat-wireless-2.6-stable/v2.6.38/compat-wireless-2.6.38.2-2.tar.bz2
$ tar xvf compat-wireless-2.6.38.2-2.tar.bz2
$ cd compat-wireless-2.6.38.2-2
$ ./scripts/driver-select ath9k_htc
$ sudo make
$ sudo make install

That's pretty much it. I suspect other up-to-date versions of compat-wireless will also do the trick, but for now - this does just fine.