- Some zero-install apps at http://www.svsdownloads.com/
- Can install an app on one machine and run it on another. If the app requires activation based on your hardware, you'll have to activate it on multiple machines.
VMWare (and other VMs)
- Can run apps installed to an image.
- Slow, and really needs more than 1GB RAM and faster than a 1.8GHz mobile Pentium on the PC. Ubuntu is slow, Kubuntu is slow. I still want to try XUbuntu and running Ubuntu non-GUI with a Cygwin X-server.
- Sometimes you have to re-activate -- if you have an app that requires activation on hardware changes, and you run it on a major-different processor
- Limited selection of apps
- Run on any PC from your USB drive
CoLinux seems to run pretty well, but I can't use it at work. They've used a Group Policy to block ICS NAT, and since Windows XP sends STP (layer 2 routing protocol) packets it could get my network port shut down. Then I'd have to explain why. Also worth noting, X-windows won't run on CoLinux, so you have to run your X-server in Cygwin.
Update: I got the latest snapshot of CoLinux and configured a network proxy virtual NIC. It works pretty well.