PortableApps.com
This nomination is courtesy of Chamunks Arkturus.
PortableApps.com allow you to run a wide variety of Windows software (much of it FLOSS) off a USB key or other device without writing to the local hard drive. The PortableApps packaging software itself is open source.
John Haller, the founder of PortableApps, has made a personal appeal for donations. One of the blog comments indicates that the organization spends $25 000 per year for hosting alone.
The donation page for PortableApps.com is .
Contribution
$26.30CAD = $26.00USD