One very powerful yet often overlooked feature of the iPhone is the spotlight search. Spotlight search is accessed by pressing the home button when on the home page or by going to the page to the left of the home page.
As soon as you start to type the results will begin to thin down. Once you see the app, contact, song, video, email, or appointment that you want, just tap it.
For apps this can be much faster than flipping throug pages of icons. The same applies to contacts.
In iOS4, spotlight search was expanded to add text messages (SMS and SMS) plus options to search the web and search Wikipedia. It also adds the most often chosen result at the top of the list, with the label “Top Hit”.