opera and firefox are good portable browsers.
theres a portable browser called browzar which is based on the IE engine. its selling point (though its free) is that it is completely private. it doesnt save cookies, temporary files or anything for that matter so theres no trace of your browsing activity. but the drawback is that since it doesnt use temp files and such, its really slow. but its great for ur privacy if ur using some public computers to check ur mail or such activities. if u r ready to sacrifice speed for privacy, go to *www.browzar.com/ and get it from there.