Browser extension (for Firefox currently) which allows you to get a preview and summary of the linked page, while hovering on a link. Quite useful for link-heavy pages like you have in Trac, or when you want to quickly get more details about tickets from a ticket query (see #10383).
Unless I'm severely mistaken, you can see in the above that they even have special support for Trac!
Lines Modified and
Total Lines Altered are nowhere to be seen in the changeset page HTML source; OK, the count of lines is not really exact, but nice try ;-) )