This post is mostly for my reference and for an associate who wanted to see an updated list, but hopefully it is useful to others as well. :)

Theme:

Name	Description	License	Development
Oxygen KDE	Imitates KDE's Oxygen style.	GPLv3	Inactive

I have a slightly modified version available for download which allows you to install it on recent versions of Firefox.

Additionally, I have a screenshot available if you would like to see how it looks.

Edit: Unfortuately, the Oxygen KDE theme no longer works properly as of Firefox 29. I tried using it with the Classic Theme Restorer extension and while some of it works there are obvious issues with the theme which need work.

Extensions:

Extension Name	Description	License	Development	Restart
Adblock Edge	A light-weight fork of the Adblock Plus extension.	MPL 2.0	Active	No
BetterPrivacy	Removes Flash "Super-Cookies" / LSOs (Local Shared Objects)	Freeware	Inactive	Yes
Blender	Blend in the crowd by faking to be the most common Firefox browser version/OS/etc.	WTFPL	Active	No
Clean Links	Converts obfuscated/nested links to genuine clean links.	MPL 1.1	Active	No
cliget	Download protected files using curl or wget.	MPL 1.1	Active	No
Cookie Controller	Buttons for managing cookies, cookie permissions, and site cookie exceptions.	MPL 2.0	Active	Yes
Disable clipboard manipulations	Prevents websites from interfering with copy and paste actions.	MPL 2.0	Inactive	No
DuckDuckGo Plus	Adds DuckDuckGo as the default address bar, search bar and right-click search engine.	Apache 2.0	Active	No
gfycat Companion	Converts .gifs to HTML5 video for faster loading.	MPL 2.0	Active	No
Greasemonkey	A User Script Manager for Firefox	MIT/X11	Active	Yes
HTTPS-Everywhere	Encrypt the Web! Automatically use HTTPS security on many sites.	GPLv3	Active	Yes
NoScript	Blocks JavaScript, Java, and other plugins on all sites except for domains of your choice.	GPLv2	Active	Yes
Privacy Badger	Protects privacy by evaluating third-party sites and blocking those that appear to be tracking you.	GPLv3	Active	Yes
Reddit Enhancement Suite	A suite of tools to enhance Reddit.	GPLv3	Active	No
RedditNotifier	Notifies you of new messages on Reddit.	MPL 2.0	Active	No
RequestPolicy	Control which cross-site requests are allowed. Improve the privacy of your browsing.	LGPLv3	Inactive	Yes
Self-Destructing Cookies	Protects against trackers and zombie-cookies. Gets rid of a site's cookies and LocalStorage as soon as you close its tabs.	GPLv2	Active	No
Smart Referer	Send referers only when staying on the same domain.	WTFPL	Active	No
The Addon Bar (restored)	Restores the Addon bar on Firefox 29	MIT/X11	Active	No

Userscripts:

Name	Description	License	Development
Bypass YouTube age verification Improved	Bypasses YouTube age verification without logging in.	GPLv3	Active
Disable NoParticipation	Cancels the NoParticipation CSS on Reddit without redirection.	Public Domain	Inactive
Github - CoderStats	Adds a link to CoderStats on a user's page.	WTFPL	Active
GitHub - Open Source Report Card	Adds a link to The Open Source Report Card on a user's page.	WTFPL	Active
GitHub repository list sorter	Adds options to sort the list of repositories on a user's page by name/language/stars/score.	Unknown	Active
Greasy Fork	Enhancement for the greasyfork.org Userscript site.	CC BY-NC-SA	Active
Mail Context Script	Shows the context of received messages to your Reddit inbox.	Unknown	Inactive
Reddit Tidy	Remove some cruft from Reddit's interface	Public Domain	Inactive
Straight Google	Remove Google's URL track redirection from Google Products.	GPLv3	Inactive
Userscripts.org Scam Filter	Filters out scam scripts at Userscripts.org	Unknown	Active
ViewTube	Watch videos from video sharing web sites without Flash Player using HTML5's video player.	GPLv3	Active
YouTube Ratings Bar	Shows ratings of related videos on Youtube	Unknown	Inactive

If you have interesting Firefox extensions or Userscripts (preferably open source), please feel free to post them in the comments section below.