Number 6 on "My Top 10 Most Useful Free Programs" is FileZilla FTP Client (Available at http://filezilla-project.org/)
FileZilla is a free FTP client. For those that do not know what that means, It is a program that allows you to transfer files between your pc and other computers on the internet. This comes in handy for those that create their own websites and need to send files to a web server.
The user interface is fairly simple.
Filezilla allow you to save multiple profiles that allow you to easily switch between servers you connect to.
On other feather I like about this software is the ability for it to connect using SFTP and FTPS. This is the secure method of transferring files over ftp. Think of it as HTTPS of FTP.
For those of you that like to take your programs with you on a USB key or other removable there is also a portable version available that work the same way.
You can download that version from Portableapps.com
And for those that would like to run their own FTP server there is a Server version available at the web site.