PortableApps are popular software, optimized for portable use, and packaged in the PortableApps.com Format, so you can run them from an iPod, USB flash drive, portable hard drive, CD or any other portable media. You can take all of your settings and data and no personal information will be left behind on the machine you run it on.
You can find official PortableApps releases on PortableApps.com. These packages have been thoroughly tested and reviewed by the PortableApps.com team.
If you can’t find the app you’re looking for, try the Test Releases. Keep in mind that these should be handled with care as they are not yet fully stable.
Here are some other really good (unofficial) PortableApps packaged by other developers in the PortableApps.com Community: