I played with Greasemonkey a while back, and thought it was really interesting, but I couldn’t come up with a lot of practical applications for it at the time. The add-on came up in a conversation I was having with someone, and as a result I decided to revisit it. I still haven’t come up with anything amazing to do with it, but I have been finding it increasingly helpful to cutout a few clicks in my daily web browsing. For example, I now have it submit forms on login pages to automatically log me into sites I visit often. I also have it setup to navigate to a page from a site if I often go to the same page after login. For example, maybe you get dumped to a landing page when you first login, but you always want to go to a specific section right after that. In this case, I’d setup a script to run on the page that I land on that automatically takes me to the second page (that I really wanted to go to) instead. These kind of things might sound silly, but most often they’re a single line of js and they can save me a couple clicks a day. Those clicks add up! Not to mention the ease of use factor, since I don’t have to be annoyed by the fact that I have to find the silly link every time I login.
For any of you out there that know even a hint of JS I’d really recommend checking it out. It can be a great time saver on these little, trivial things and make your web browsing that much easier.