What, you don't like the bookmarklet that Omni provided in the latest release to do this very task? :)
From the release notes for OF 1.6 for iPhone:
OmniFocus can now accept tasks from other applications! As a demo of this functionality, there's now an "Install Safari Bookmarklet" option under Experimental Settings (to install a bookmarklet which sends your current web page from Safari to OmniFocus).
I use the Mail Link to this Page option in Safari rather than making my own message as you do, or using the bookmarklet, if I'm likely to add more than one URL. It doesn't launch another application (such as OmniFocus or Mail) so I don't have to relaunch Safari, and with my Mac set to check Mail every minute and sync a minute after a change, I can usually finish up in Safari, launch OmniFocus and the auto sync on launch will grab those new items. If I only have one thing to add, or I want to make some notes right away, then I'll use the bookmarklet.