One of the features I use from time to time in Photoshop CS is the Filter: Pattern Maker... option. In summary, this allows you to define a new pattern stamp using a portion of your image. As time went on, I noticed the time to load Photoshop was getting slower and slower. Turns out that some of the patterns I defined were rather large, and because Photoshop caches them each time it boots, there was a long delay as it loaded each pattern.
The solution is to periodically purge any custom patterns you are not using, so they are not loaded each time Photoshop is started. To do this, perform the following steps:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051204082356184