TOP 26 Ubuntu Application Sources

There's what seems like a half-billion applications for Linux that work on Ubuntu. And honestly, that's a lot to go through. So, I decided to compile a list of some of my favorite sources for Ubuntu applications. Enjoy, and feel free to add your favorites in the comments!

1. The Daily Ubuntu - a daily updated source for Ubuntu Applications.
2. Lifehacker's Top 10 Ubuntu apps and tweaks - Top 10 Ubuntu applications list from Adam Pash of Lifehacker.
3. Lifehacker's Top 10 Ubuntu Applications - Another Lifehacker listing: "our favorite ten Ubuntu software applications that are exclusive to GNU/Linux"
4. Installing Popular Applications On Ubuntu - a few notes.
5. Installing Popular Applications On Your Ubuntu Desktop With Automatix2 - Guide on using Automatix2, an automatic program installer for Ubuntu.
6. GetDeb - Ubuntu Software Portal - A repository of Ubuntu software in .deb format.
7. 35 Cool Applications to install on Ubuntu 7.04 - How to install 35 good Ubuntu applications not shipped by default with the operating system.
8. 13 Applications to Install on Ubuntu running on Slow Computer - Optimizing and using Ubuntu applications under a low RAM environment.
9. ExtremeTech: Applications Included with Ubuntu - a discussion of some of the default applications.
10. Ubuntu Applications - Occasionally has some Ubuntu application information.
11. Install Popular Applications in Ubuntu Feisty Fawn Using Automatix2 - Another Automatix2 guide.
12. Applications Guide - Community Ubuntu Documentation - An applications guide from the Ubuntu wiki.
13. Little Ubuntu >> Awesome Ubuntu/Linux Apps you not know about - Some more obscure programs (many of which, like feh, run well under low RAM).
14. Ubuntu applications for slow systems - More low RAM Ubuntu programs.
15. Ubuntu Guide - Directions on how to install a wide variety of Ubuntu applications, plus plenty of other stuff.
16. Applications on Ubuntu Linux - a wiki list of selected Ubuntu Applications.
17. 17 Must have applications for the Ubuntu user - includes a wide variety of Ubuntu programs.
18. 17 (more) Must-Have Free Apps for New Ubuntu Users from Free Geekery - a very good list.
19. Some applications I have in my Ubuntu (Dapper Drake) - one user's list of preferred applications.
20. Sound & Video Applications from the official Ubuntu wiki - includes links to the application's website as well.
21. The Best Ubuntu Applications - Another user's list of favorite Ubuntu applications.
22. GNOME Files - Software repository for GNOME. Most will work for Ubuntu.
23. KDE-Apps - Great if you use Kubuntu/KDE.
24. Cool applications you use that others might not know of, from Ubuntu Forums - Great user generated Ubuntu application list.
25. Top 10: Your Top Ten Packages To Install - Another great list from the Ubuntu forums.
26. Top Ten List of Software YOU Need in Ubuntu Linux - check out Screenlets on this list. I've not used it yet, but it looks really interesting. Also, view the related Ubuntu forums post here.
    

BONUS: Ubuntu packages site - Last but not least, this site is the official listing of all of the packages available for Ubuntu in the repository. It's a source you definitely need.