First my ever growing list of PortableApps links at del.icio.us: http://del.icio.us/DecoyFlyer/PortableApps
Next I give you several of my favorites:
- The Portable Freeware Collection
- Wikipedia's Portable Apps List
I will get into more detail another time, but for now check out the links, and remember i have not tested all of the programs they have, so use them at your own risk.