FTP (File Transfer Protocol) is an access method which is specialized for the transferring of files, or binary data. FTP sites begin with the ftp:// prefix and look somewhat like the hard drive of your computer, as they have files scattered in many different directories. To visit FTP sites, you can probably use your browser (Netscape Navigator/Communicator and Microsoft Internet Explorer both have the ability to view FTP sites) but you may wish to use a FTP program instead. The most popular FTP programs are CuteFTP and WS-FTP (WinSock FTP). Both are available from most shareware sites, in addition to the ThinkQuest CD (cdromdrive:\web\winware\index.htm -> select the FTP link). Both programs make it easier to navigator FTP sites by using an interface similar to a Windows File Browser. For those of you with Macs, the ThinkQuest CD should contain at least one FTP program that you can use. Quarterdeck Internet Suite includes a FTP program called QFTP. It is similar to the others mentioned here.
Well, now that you know how to get an FTP program, you're going to need some sites to visit. To search through a database of FTP sites, try http://www.filez.com. There are catalogs of programs listed right along with the search engine. Also try visiting different sites and looking for something about an FTP site or server. The list below has some FTP sites that you may wish to visit.
Microsoft - Microsoft's FTP site (has lots of stuff)