Useful tips I found to speed up iPhoto

Vacuuming iPhoto database (MacWorld)

Using a terminal program, get into the iPhoto library directory, then run this command

for dbase in *.db; do sqlite3 $dbase "vacuum;"; done

Rebuild iPhoto Library

Hold down <Option> and <Command> when starting iPhoto. When greeted with the Rebuild Photo Library dialog, check the “Rebuild all of the photos’ thumbnails” and the “Examine and repair iPhoto Library file permissions” boxes.