Update: I should have known it would be easy. As Bryce points out "Or tap the address bar and tap the share button at the top-left." ... Sometimes I wonder how I manage to operate these things...
I'm sure it's already been reported somewhere, but I don't remember seeing it, and I just thought of it, so I'm going to pass it along. Feel free to tell me in the comments that this was figured out the day after the iPhone was released.
Anyway, have you ever been browsing on your iPhone, and wanted to send the url off to someone via email? Well, since the iPhone has no copy + paste... your mostly SOL. Enter this handy little bookmarklet:
View a page, hit that in the bookmarks, and it'll open up Mobile Mail with a new email message, and the url as the body.
Totally off topic, but Jotit is cool.