This is a very simple tip that I like to do every couple of months to speed up the opening times of iPhoto. Everytime I carry this out I notice a significant improvement. I also do this when I upload a large number of photos like I have just done after my holiday.
Before you click on the iPhoto icon then hold down the option (alt) and the command keys (cmd), for new mac users they look like......
Option Key Command Key
Now when you click on the iPhoto icon you are faced with a menu like the one below
I always choose these options, but you can just choose the top two. This does take a short while, but it can help with your opening times.
I am always interested in feedback so feel free to add any comments, or you can mail me here, also if you would like to submit a quick tip with full credit and links back to your site then also feel free to contact me.