Attend and OpenStreetMap speaking engagement or mapping event in your town. Or organize a mapping event for your town.

Did your josm Yahoo! WMS plugin break when you upgraded to Firefox 3? Firefox 2 was just fine. What happened?
I dunno. Must be something serious.
You are not alone. Here's a quick hacky workaround to get you going again.
This is a dirty rotten hack and should not be considered by anybody. On the other hand, it is a relatively quick and easy dirty rotten hack. Use your judgment.
Use Seamonkey instead of Firefox 3 for the josm YWMS plugin. Use Firefox 3 for your browsing.
sudo apt-get install seamonkeyPlease note: On Ubuntu Hardy, Seamonkey from apt-get was version 1.1.12, and the latest from seamonkey-project.org was 1.1.13. Both worked.
On Ubuntu Feisty, I used iceape for the apt-get and the executable, rather than seamonkey. This worked as well.
Seamonkey provides binaries for several common platforms so Linux, Mac and Windows users should be all set.
This worked at a mapping party on a Windows box. Using Seamonkey was easier than juggling Firefox profiles between Firefox 2 and Firefox 3.
This fix was presented to me by Kevin, one of the attendees of the DC area mapping party from November 1-2, 2008. Thank you, Kevin!