Operating Systems
Ubuntu – Debian Based and my personal favorite – extremely easy to install, configure and useKnoppix
PCLinux
Damn Small Linux
Gentoo
Suse Linux
Mandriva Linux – Also very easy to install and use
Redhat Linux – very flexible and comes in numerous configurations for desktop/workstation, server, enterprise server, etc.
Anonym.OS – Only available as a LiveCD that is used to boot the computer and run it from CD. Very useful if you need to be TOTALLY ANONYMOUS or are just a Privacy Fanatic. Maybe possible to install but not sure.
Slackware – very popular but not the easiest to use/learn
FreeBSD – based on BSD (Unix)
OpenBSD – based on BSD (Unix)
Applications
Business
Quasar Accounting – Replaces Quicken/Quickbooks – NOT FREEQuasar Point-of-Sale – Runs Cash Registers and ties it to your accounting software – NOT FREE
GnuCASH – Replaces Quicken/Quickbooks
BANAL – Book Keeping System
Graphics
Dia – Diagram EditorgThumb – Image Viewer
Blender 3d modeller
Gimp Image Editor
Kooka
Wings3d – 3D mesh modeller
Internet
aMSN – MSN Messenger for LinuxaMule – eMule P2P Client
Bittornado – Bittorrent client
Direct
Connect - P2P Network/Client
Epiphany Web Browser
EtherApe – Graphical Network Monitor
Ethereal – Network traffic analyzer
Firefox
Galeon Web Browser
GnomeMeeting – similar to Microsoft's NetMeeting
Konqueror Web Browser
Kopete – Trillian Style Instant Messenger for AIM, ICQ, MSN, Yahoo and more
Linphone
– Skype style VOIP Telephony Program
Mozilla Mail Client
Mozilla Web Browser
Nicotine – SoulSeek network filesharing client
Thunderbird Mail Client – Similar to Microsoft Outlook
Office
AbiWord Word ProcessorAdobe Acrobat
Reader
Mozilla Calendar
OpenOffice.org Suite – Replaces Microsoft Office
Other Cool Applications
Celestia Space SimulatorGNOME
Predict – Satellite tracker
GRAMPS Genealogy System
Programming
Anjuta IDE – Integrated Development EnvironmentBluefish Editor – Web Development Editor
Boa Constructor – RAD Tool for Python and WxWindows
Eclipse – Integrated Development Environment
Gazpacho
Interface Designer – Design Graphical User Interfaces
gPHPEdit – Edit PHP source files
Quanta
Plus – Web Development Environment
Screem
HTML/XML Editor – Website Editor and Management System
Multimedia
amaroK – WinAmp on SteroidsAudacity – Record and edit audio files
GnomeBaker – Burn CD/DVD discs
Gnomoradio Music Player – find, download and play free music
Grip – CD Player/Ripper
Helix Player – very good media player
K3B – CD Writing Program (Does DVD's Too)
Mplayer – Very easy to use and no fuss media player
Nomad Jukebox Manager – Upload, Download and Edit tracks on your Creative Nomad
Ogle – DVD Player with Menus
RealPlayer Video Player
Serpentine – Create audio CDs from Music Files
VLC for Gnome – Media Player
System and Security Applications
Firestarter – Desktop Firewall ToolGnomePGP – PGP Encryption Program
Synaptic Package Manager – The best package manager on EARTH.
Special Note: If you install a version of Linux like Debian or Ubunto that has the Synaptic Package Manager preinstalled you can use it to find all of the software listed above and much much more. Plus you can select numerous programs from the package manager and have then all automatically installed and configured, including dependancies. It is now as easy as Windows/OSX to install software using the Synaptics Package Manager. Plus the package manager has a WindowsUpdate style feature built in that will check and prompt you whenever there are updates to any of the operating system or software installed on your computer.