Not sure if I got frustrated, creative, generous, or all of the above. I made a web form called iPastelet Maker that lets you easily create custom bookmarklets that paste text into web forms on the iPhone. Use it to create bookmarklets for common recurring entries, like user ID's, email addresses, IP addresses, host names, etc. You might even create a bookmark folder called 'Scrapbook' and keep a bunch of common text snippets there. If you have a few services/servers you log-on to and use the same email/ID's over & over this can be really convenient.
Since they are bookmarklets, they obviously only work in a browser, and work best in Safari/Mobile Safari. However, it is best to create them with your desktop browser (preferably Safari on Mac and IE on Windows). Then, use iTunes to sync your bookmarks over to the iPhone and voilá.
It's free stuff, so feedback is welcome, but support is nil. Thanks to TUAW and Erica Sadun for awareness, code and inspiration.