A while back we mentioned a neat trick for speeding up Mail.app by "vacuuming" its SQlite database. Now the original source of the tip, Tim Gaden over at Hawk Wings, points to Leland Scott's VacuumMail, which utilizes a little AppleScript and launchd to automate this process. Tim also notes that if the default time of 1pm on Tuesday isn't to your liking, you can change it using Lingon.
VacuumMail is a free download.
[Via Hawk Wings]