Software

1. Open Source Alternatives (to closed/proprietary software)
   http://www.osalt.com/
   A newer site that suggests open source alternatives to popular closed source programs

    

2. Table of Equivalents (of Windows software in Linux)
   http://www.libervis.com/wiki/index.php?title=Table_of_Equivalent_Software
   A table that maps popular programs on the Microsoft Windows platform to programs that run on the GNU/Linux platform... This is very helpful when looking for software to replace a particular program.

    

3. Apache
   http://www.apache.org/
   The most popular web server on the Internet since April of 1996.

    

4. Freshmeat
   http://freshmeat.net/
   A cornucopia of (mostly) open source software, tracking latest versions and vital links. Browse by categories, search or go random!

    

5. Gimp
   http://www.gimp.org/
   A freely distributed piece of software suitable for such tasks as photo retouching, image composition and image authoring.

    

6. GNOME
   http://www.gnome.org/
   A free and easy-to-use desktop environment for the user, as well as a powerful application framework for the software developer.

    

7. KDE
   http://www.kde.org/
   A powerful Open Source graphical desktop environment for Unix workstations.

    

8. Linux Kernel Archives
   http://www.kernel.org/
   This is the primary site for the Linux kernel source, but it has much more than just kernels.

    

9. Linux Terminal Server Project
   http://www.ltsp.org/
   Run thin client computers in a GNU/Linux environment.

    

10. List Of Open-source Programs (LOOP)
    https://wiki.ubuntu.com/LoopList
    A list of high-quality Open Source programs for the Windows environment.

     

11. Mozilla
    http://www.mozilla.com/
    Mozilla Firefox is an open source web browser, designed for standards compliance, performance and portability.

     

12. OpenOffice.org
    http://www.openoffice.org/
    An open-source, international office suite that will run on all major platforms.

     

13. Samba
    http://www.samba.org/
    An Open Source/Free Software suite that provides seamless file and print services to SMB/CIFS clients.

     

14. WINE
    http://www.winehq.com/
    Wine is an implementation of the Windows Win32 and Win16 APIs on top of X and Unix.

     

15. X
    http://x.org/
    A freely redistributable open-source implementation of the X Window System which runs on UNIX(R) and UNIX-like operating systems (forked from XFree86 after a controversial license change).