My Screenshots-Portabe software page: Software working i many platforms (GNU/Linux Wintel NetBSD on Alpha etc.)!
Note: Some browsers scale the images by default. Prefer to see them in their actual size. 



Celestia Free Space Simulator
Celestia, The free 3 dimensional space simulator!
Here I travelled to Saturn, also displaying the planet and satellite orbits. Running on KDE 3.4 on Slackware 10.2
Celestia Free Space Simulator Gcompris, an educational application for small (or older like me) children is running on my Windows 7 Desktop.
Celestia Free Space Simulator Mozilla Firefox runs almost anywhere! Here wearing the "Clean W" persona (theme) while browsing for others! Running on KDE 4.2.4, X.org 1.6.3, kernel 2.6.29.6, Slackware 13.
Openoffice Suite
Former Sun Microsystem's child, and originating from StarOffice, compatible to Microsoft Office file formats and having also its own Open Document Format PLUS a PDF export feature, Openoffice.org is a complete Office suite excellent for everyday's work. Here running on Windows 7.
Xmind
As Wikipedia says: XMind is an open source brainstorming and mind mapping software tool developed by XMind Ltd. It is a"Getting things done" structured chart-diagram designer supporting cause-and-effect, completion, relationships and trees. A built-in tool connects users and permits central server-based sharing - to view or edit. A portable multi-platform package exists.



This is a page for portable projects i.e. software that is designed to compile and install in multiple platforms.
But: a program that's not portable as a project, but may still have a "portable version" available for downloading.

A very "clean" definition of a project's "portable version" or "portable package" is that the project can reside in a directory and function without the need of an installation method.
Although this is the general idea, some programs need more than this i.e. one-time install to a usb stick along with OS prequisites and sometimes special portable stick technology and/or installer.
But XMind has a "clean" portable version. I use the decompressed portable package both in Win7 and Slackware Linux 13.1, as it includes all its OS variations inside the zip archive!!


For GNU/Linux, it is best to uncompress a portable app in a relevant dir like /opt as root AND then place a soft link of the app in a binary dir that is on the path i.e. /usr/bin or better /usr/local/bin
For Windows 2000, XP, Vista, 7, program directory placement inside
Program Files by the Administative user(s) AND a shortcut to the "All Users" menu is sufficient.

Some other portable (cross-platform) projects that I didn't mention here:

Mozilla Project Firefox aside, Sea Monkey suite, Thunderbird, Sunbird & Lightning, Camino & Bugzilla.
KDE
Always portable for Unix related OSes, now cross-platform with Windows and Mac OS X!
Gimp Image processing-editting application.
Picasa Web enabled album creation application with editing-optimising enhancements.
MPlayer
Media backend, with internal & external frontends, in Linux, Windows, MacOS X etc. even QNX & BeOS!
Videolan VLC
Media player & streaming software.
VirtualBox Very powerful virtualization software. Special notes here.
Pulseaudio
Network-enabled sound server.
Apache
Web server suite.
Dosbox Multi-platform DOS emulator.