Use Safari in Landscape Mode
You zoom in and out in Safari using the multi-touch screen and when zoomed in you can just drag your finger around the screen to scroll. But when you're reading, you don't really want to keep scrolling to read each line of text. When the iPhone is held in landscape mode, the screen is wider and content doesn't get shrunk as much to fit the width of the browser, meaning you don't have to zoom so much. Granted, you do have to scroll down more frequently, but at least you've got a decent shot at all the text of a line fitting on the screen.
Safari is also the only iPhone application that supports using the onscreen keyboard in landscape mode. This makes typing much easier and faster for most people because the virtual keys are bigger and better spaced for typing with both thumbs (as on a Blackberry). For this reason, if you have longer emails or notes that you need to type, you might want to consider using a web application such as the gOffice (http://goffice.com/) web-based word processor, which is designed for the iPhone, or a webmail client such as Gmail or Yahoo Mail. Hopefully, Apple will make landscape typing available in every application soon.