FileZilla is a popular free FTP client, it is one of the must have free software out there. Portable FileZilla is a lite version of the Filezilla to use it from portable devices like USB drives, iPod and others.
This version brings all the features of latest Filezilla 3.0.11.1 with improved installer and better free space calculation. It can be installed in English only version under 3MB.
Download from Portableapps.com

An absolute must-have tool for bloggers and webmasters. Even better now that it is portable!
@Syahid
Yes the portable version is really useful
FileZilla is the best FTP client. Portable Version looks nice