there are now Mason and Executer
Executor lives in the sandbox
https://addons.mozilla.org/en-US/firefox/addon/13243
With this extension you can write javascript-based scripts for any site or single page. It means that you can add your elements of interface or hide already existed. Also you can add your stylesheet tables and apply it to any element.
But executor's capabilities not limited by interface only - it limited by your javascript knowledge.
All preferences, scripts and css stored in profile directory in executor.sqlite. If you need export it just copy this file.
Mason
https://addons.mozilla.org/en-US/firefox/addon/10636
http://blog.sociz.com/tiramn/
Mason, however, seems to have greater potential
This extension has functions as below
1. Scriptable
It is similar to Grease Monkey.
As it is loaded before any file loading, it may be more powerful and cleverer.
Please visit support site to download more scripts.
2. Http Request Redirection and Block
3. Cache any file and save to specified file path
4. Modify cookie
5. Modify referrer(custom site or site root)
6. Make Firefox show pop up dialog box to specified files
7. Fake IE6
8. Support Force content-type and Refcontrol rules import
Based on the above function, the following rules are predefined
1. make firefox "know" torrent file correctly (active by default)
2. download tudou,youku,youtube video, myspace audio files to specified path(inactive by default)
3. show pics from 163,qq,yupoo,filckr and so on correctly even cross the domain(active by default)
4. be able to visit YS168 which is an IE-only site without IE-tab (active by default)
