If iPhoto is taking a long time to start, you can speed it up by tidying up the database that iPhoto uses to keep track of all your photo information. To speed up iPhoto, here are the steps you need to take:

1) Close iPhoto

2) Open the terminal app (found in Applications -> Utilities).

3) In the terminal app change into the iPhoto directory. If you are using the default directory this command will be:

cd ~/Pictures/iPhoto\ Library

If you have moved your iPhoto library into a different place, adjust the command accordingly.

4) In the terminal, run the following command:

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

5) Restart iPhoto and be amazed at the performance increase.

reference: http://www.macosxhints.com/article.php?story=20090227072825458