I've been using Ubuntu as my primary OS since Feisty alpha 3 (Dapper was fine, Edgy was just too edgy) and I've run the development release ever since. Initially this meant I was reinstalling every month or so as an update borked by system, but since then I've been able to fix most problems I come across.
I normally hang around in the Testing and Discussion area of ubuntuforums.org. Last release I was tracking FGLRX and xorg-server changes. I also try to help out with UK English translations on Launchpad, though that has taken a back seat recently.
Contributions in brief
Tracking fglrx (AMD Catalyst) and getting it to build on Ubuntu+1 around any breakages caused by kernel or xserver upgrades (mainly Ubuntu Forums-based).
Localisation to UK English on Launchpad.
Various bug reports and a couple of patches. Various how-tos (links below).
Previously active on askubuntu.com, where I was in the top 10% of users!
Launchpad page: https://launchpad.net/~jfernyhough
Ubuntu Forums: http://ubuntuforums.org/member.php?u=143103
IRC: jonathonf on freenode.
Ask Ubuntu: http://askubuntu.com/users/4596/Jonathon
I'm currently testing GNOME3 on Natty (nvidia) and Oneiric (fglrx). This will be my main focus.
Tracking fglrx; I'm currently running Catalyst 11.5 with 2.6.39 and am waiting for the Oneiric forum to open to post build instructions.
Links to my threads
All threads: http://ubuntuforums.org/search.php?searchid=81115024