The first thing I was recommended when i bought my mac was to install quicksilver on it.
And so I did. That really proved to be the best thing to do. QuickSilver is much more than an app launcher. For me it the central point of control from where i control my whole mac.
If you are not using quicksilver yet, read these two articles to get started.
http://vjarmy.com/archives/2004/03/quicksilver_a_b.php
http://vjarmy.com/archives/2005/02/quicksilver_fro.php
And amaze your friends with you mac wizardry.