I found a Safari plugin by the name of Creammonkey, which is more or less an attempt at bringing Greasemonkey's abilities to Safari's side of the fence. For those unfamiliar
services, such as enabling colored labels in Gmail or displaying in-bound links for a site you're visiting.
It's hard to argue that the idea of adding functionality to websites isn't cool. Even in its infancy, the promises of Creammonkey sound really slick, but my one problem so far is: where are the scripts? Creammonkey is more or less a platform, and I'm having a really hard time tracking down any scripts to plug into it - including those pictured in this screenshot I borrowed.