This script makes it trivial to get a shortened URL for whatever page you happen to be browsing - just press SHIFT+T and it pops right up (or goes directly to your clipboard if you've let it*). This helps facilitate sharing links like optimized searches, maps, other really long URLs without worrying that your email or messager will break its syntax by wrapping or escaping characters.

The author is very receptive, updating the script with whatever recommendations come by. The script description could use a little more elaboration, but that doesn't detract from this being perhaps the most useful script I've come across.

* See my comment for a warning about giving Greasemonkey (all JavaScript, actually) access to your clipboard