Outlook endless Beach Ball resolved
I too started having problems with the Mac beach ball appearing every 2-3 minutes for about 15 seconds, regular as clockwork. This started happening around the time that my database got damaged and had to be rebuilt.
After some research, I realized that this was happening at the same time as Outlook for synchronizing with Exchange (we're using a remote, hosted service.) Also, I had a yellow triangle error on the far right side of the status bar. Double-clicking it showed a number of synchronization errors. I highlighted them all and deleted them, then left the window open and watched. Sure enough, the beach ball appeared and the window filled up with sync errors, all of them calendar appointments that could not be sync'ed. Unfortunately, there is no information shown about the date/time of the offending appointment
So over the next 1/2 hour, I tracked down each appointment based on the Subject text only, some going back 2-3 years and deleted it. Now, I don't have any sync errors and the beach ball seems to have disappeared!