I know there is the Firefox portable that we all know and love. However, there is a webkit browser that was featured on Lifehacker. It is lean, mean, and open source. I think that a portable webkit browser is something PA.com needs. (1) It allows web developers using Nvu or KompoZer to test websites in webkit portably. (2) It would start up faster than Firefox. Useful for a quick check on something before one leaves. (3) PA wouldn't be much of a platform without choice.
I also realize that this was mentioned before (https://portableapps.com/node/17334). However, it is out of date and the download link is broken. I think the topic needs revitalization.
Arora Browser: http://code.google.com/p/arora/