The Tor Project has released two portable software bundles. The Tor Browser Bundle contains Tor, Vidalia, Polipo, Firefox, and Torbutton. The Tor Browser IM Bundle contains Tor, Vidalia, Polipo, Firefox, Torbutton, Pidgin and OTR.
Tor Browser Bundle (binaries in several languages and install instructions here)
https://www.torproject.org/torbrowser/
Tor Browser Bundle: Details (contents, source code, signatures and build instructions here)
https://www.torproject.org/torbrowser/details.html.en