K-Meleon
Jason Foss created a very nice macro managment script for us to use on the website: it allows users to submit new macros and add comments/reviews of the macros. Browsing this big library (more than 40 macros listed!), you'll discover a lot of interesting macros to expand the power ok K-Meleon!
If you want to write your own macros, you probably should read the Macro Language Chapter of the K-Meleon User's Guide and Reference Manual.