To begin with, I'm using a Google Apps account as a primary account, and am running 2.2 on a Samsung Captivate, non-rooted. I have Picasa Web Albums checked off under account Sync, and can see my web albums in the Gallery, however, I can't share pictures to Picasa, it's missing from the 'share to' list. Does anyone have any idea how I can set this up?
Found the problem. It's not that Picasa wasn't there as a share option, but rather it was not visible. There were too many items installed that offer this intent, and the Gallery application does not have a scrollable menu. This is apparently a known bug and it's been there for quite a while so it doesn't look like it's going to get fixed either. I now use a different application for sharing to Picasa.