FlashFXP is probably the best GUI-based FTP program ever made. Supports virtually all FTP features, including direct FTP-2-FTP (=FXP) transfers, SSL connections, has an excellent site manager (that includes upload/download stats for each site) and tons of other features.

Program is also extremely small, easily customizeable (beginning from the basics, such as split-view or Explorer-style view), secure (each site can be protected with your unique password in addition to normal site passwords) and reliable. I've been using this client since late 1990's and I've never, ever even considered changing to any other FTP client after this tool.

Only complaints I have are related to some features that I would like to add into this tool -- namely multi-thread transfers. But as I know that the developer is working on bunch of new features, I'm kinda hopeful to see those final requests to be implemented into this excellent piece of software soon.

Trial version is fully functional -- only nag in trial version is the splash screen when you launch the software, but that's it. For $25, I can recommend everybody to register this tool if you need to use FTP in your everyday life. As a good reference -- this site has been/is developed using FlashFXP as a secure FTP client :-)