extending Firefox

I have to type this again, because TypePad lets me wipe out my text by accidentally navigating to another page.  Anyway...

Firefox can be extended in multiple ways.
One of the easiest is the search box in the upper right-hand corner.
You can just click on the default Google G and it will pull down a list of the other installed plugins, as well as a link to add more.  I added Webster for dictionary searching (they already have Dictionary.com but I don't like it as much).

You can also of course write bookmarklets in JavaScript (which really in my head I still think of as LiveScript instead of this meaningless marketing name that has nothing to do with Java programming).

As well, you can add extensions, and create toolbars and sidebars.

And last but not least, you can make quick searches.

Everyone seems to be hot for toolbars, I'm not particularly clear why.
If it's just basic search you want, a search plugin or a quick search makes more sense.

The latest is a Yahoo toolbar.  There is also one for A9.

For some reason, this info doesn't seem to be presented all in one place.

Add search plugins:
http://www.mozilla.org/products/firefox/central.html#central-engines
Make search plugins:
http://mycroft.mozdev.org/

Quick Searches
The link I have is http://devedge.netscape.com/viewsource/2002/bookmarks/
unfortunately this is currently down for me
You can get it from the Internet Archive.

You could use this to e.g. set up an ISBN search so that you would just type

isbn 1231231231

into the Firefox address bar.

bookmarklets
http://www.webreference.com/js/column35/

extensions
This tutorial may give you some insight on making Firefox extensions
http://roachfiend.com/archives/2004/12/08/how-to-create-firefox-extensions