Here's my take on what would make a good bookmarklet. How about a tool that helps you build a standardized bibliography entry (MLA, etc.) for the webpage (people do cite webpages these days) based on elements in the header, meta data, or user selections? The URL is most definitely important. The day viewed is also important from what I hear.
So, given a webpage, a user could spawn a new window that disects standard parts of the web page for assembly into the standard parts of a webpage bibliography entry. Here's your standard parsed stuff--now, the user gets to assign chunks to the proper bibliography pieces.
The challenge is that the pieces of information will not necessarily follow a pattern you might hope for. But with a little effort, it could save you the work on all of the formatting. Heck, you might even expand the service to build a collection that could be managed by the user.
Take that all you info-organizing-hacking-tweaking-slice-and-dice-data-pundits. There's my two cents (with more cents offered daily). This should make that Shifted Librarian proud (or not).