Make a page that allows you to edit ANY document on your site using a web interface (content editable div, etc.)
Make a page/app that gives you the approximate time. "It's about three o'clock, It's a titch past four, It's somewhere between four thirty and quarter to"
Enter some text or numbers, get a barcode back
Given an image, type text in a bot and click on a section of the image and have the text appear on the image in that section. (A graffitti board)
Page for the National Sledgehammer and Broken Toe Society
Build a typical Internet conspiracy page, but the conspiracy is that the government is not out to get us, but to help us
Build a content management system to include text, graphics, and scripts
Build a headlines/breaking news system
Use the session object to track where people have gone -- lists of urls for sessions. give the session anonymous names like "mr. pink" or "humphrey humphreys" etc.
Email _from_ a friend link on web pages
Subscribe to any page on site (i.e. I give you a URL and a frequency and you email me that page at that frequency)
Enter a url and get a screenshot back.