Here are a few scripts that I have found interesting from a coding standpoint. Even if you have no interest in the particular site(s) that a script deals with, these have some interesting techniques to learn by example - both good and bad.
The reality is that Greasemonkey scripts are very fragile. Even a small HTML change on the site can blow the whole script out of the water. A unique idiom that I employ here is "Feature Isolation" via try/catch. (See dispatchFeature() and TryCatch() functions in the script.)
This script demostrates an object as an associative array. The first half of the script is the definition of the "Greasemap" object, which contains a few methods; this object in used the last few lines of the script. Unfortunately the pattern matching portion of this script does a bunch of gymnastics with the raw HTML text of the document, rather than using XPath to parse through it.
This script gives us some nice examples of functions as data, employing very cohesive idioms like comparator functions, and ties it all together with associative arrays. All in all, a very readable script given how much it does. This script also uses some of the best variable and function naming that I've seen in a Greasemonkey script.
I really think the BugSort code could be the basis for a generalized cross-site grid sort capability...