Tapping the top menu bar returns you to the top of whatever scroll area you're in. This is super useful when browsing forums in Safari
You don't need to press that cumbersome top-edge button to wake your home.. just use the home button!
They keyboard works in widescreen mode when you're using safari with the phone on its side
You're not limited to just tipping the phone to the left-- if it's more comfortable for you to look at photos or websites by putting the phone on its right edge or even upside down, that works too!
Google Reader launched an addition to its website that gives you an iphone-formatted interface by default when you go there with your iphone. Don't fool with clunky webapps, switch to google reader and bring all your sites to you!
In CoverFlow mode for your music, if you tap the absolute upper-left pixel on the display, you enter file-browsing mode where you can move/delete your music and photos.