If you're using Firefox and are finding that it seems to take ages to start up, then
SpeedyFox does a great job of optimizing the databases to make it quicker.
If you've never used this nor the
Vacuum Places add-ons before, then you could well find the difference to be quite noticeable.
I've been using
SpeedyFox with FF 3.5.3 for several weeks without a problem and it's well worth running it regularly.