Abe Fettig has written a simple bookmarklet that enables you to view source within iPhone’s Mobile Safari. It’s seven lines of javascript and it works great. I use it frequently, especially to test code that I’m serving specifically for mobile devices.
Mobile Safari’s source is small and black/white, but at least with Abe’s bookmarklet it can be harvested. For quick peeks this works great. When I need a deep analysis of some markup, I trigger the bookmarklet then copy/paste the source into an email. This enables me to pull the into Textmate and view it cleanly.