I've been using the Press This bookmarklet a lot lately. Here are some ideas for enhancements:
Define a common value for the included link - a lot of sites link to their original source using a common name, such as "Read", or "Via". It would be nice to be able to set the Press This bookmarklet to always use one of these words, instead of the name of the site you're on. It's not easy to change the link text using the current version.
More consistent media options in the bookmarklet - there are no media buttons, no image editing options, etc.
Spell checking via Press This.