The Arkansas Team has a thread where people are discussing their location, but as far as I know the best way to post yourself on a map is using Launchpad.*
UPDATE: It's 2011 and sometime since I posted this Canonical removed the map from launchpad. Now all you can enter is your time zone.
Here are the old directions:
After you are registered and logged in at http://launchpad.net/ click your username at the top right corner to get to your Launchpad information. Scroll to the bottom of that page, and click the link under the Google map that says "Set location and time zone." You will see a Google map with some directions at the top. There is no need to find your exact street location -- in or near the nearest town is fine.
Once your location is entered, be sure you are a member of Team Arkansas in launchpad so your location shows up on that map... http://launchpad.net/~teamarkansas
Thank you for setting your location! I hope we can plan some events based on where our team members live or work...
*(You can also use launchpad to report, triage and suggest fixes for bugs, and once you have a launchpad login, you can use it to log in to this forum and other official Ubuntu locations.)
**If someone knows how to make this post "sticky" please let me know.