I've found a few nice things for Mozilla Firebird, the IMHO least sucky browser right now (apart from being a memory hog).
The Permit Cookies extension does not do what its name implies, but gives you a popup for blocking/allowing/removing cookies for the current site on pressing Alt-c.
Why not allow cookies with all the other features enabled, especially "ask before accepting"? I had that, but I ran into major slowdown issues with a really big cookie permissions file which denied cookies for 99.8% of the sites anyway, and the question popup was very annoying, too.
So now I have cookies disabled in the global preferences as a good default, and for the few sites where I accept the requirement for cookies as sensible, I just enable cookies specifically for the site, once and comfortably.
Disabling cookies doesn't actually disable them: the explicit exceptions still work. The one thing I lose is the "cookies for this session only" functionality; that is taken care of by my mozilla wrapper which simply removes the cookie file on startup.
Flashblock is another saviour: flash crap is not displayed at all but a placeholder shows up. You can click on it and only then the flash thingie loads. Very nice, very useful.
The Tabextensionsextension is so common now that it has been properly Debianised - a welcome change from the lousy XPI installation mess mozilla tries to force on us otherwise.
Related to debianising mozilla and hand-installing extensions without messing everything up is this bit of info:
Mozilla on Debian gets its extension info from per-package files
/var/lib/mozilla-nameoftheday/chrome.d/. The good old
run-parts-like approach works perfectly well here, too: you (or any
package) can plop a file like
said dir without affecting any other aspect of moz,
update-mozilla-firebird-chrome to combine those
files into what moz wants to see.
So what I nowadays do to install extensions by hand but cleanly is rip the XPI apart and copy the bla.jar into /usr/lib/mozilla-nameoftheday/chrome/. Then I look at the install.js to see the register-something calls and populate my 99... fragment with the appropriate entries. Run the update program, restart moz, done.
Here's the entry dealing with the editcss extension as an example (they all look very similar):
content,install,url,jar:resource:/chrome/editcss.jar!/content/editcss/ locale,install,url,jar:resource:/chrome/editcss.jar!/locale/en-US/editcss/ skin,install,url,jar:resource:/chrome/editcss.jar!/skin/classic/editcss/