There are many FTP programs for OSX. However, these are the 2 prefer the best in their class.
If you're going the free route (donations accepted), there is no question that Cyberduck is the way to go. It features a well designed, easy to use interface with quickly accessible bookmarks. It's open source, supports FTP, SFTP, WebDAV, Mosso Cloud Files and Amazon S3.
Commercially, Transmit from Panic is king. It supports FTP, SFTP, or TLS/SSL, Amazon S3, iDisk/Webdav, Synchronization, server to server, Dashboard widgets, Droplets, the list goes on and on. Visit the panic site for a complete feature list. Transmit costs $29.95 for a single user license, and there is a demo version available for download.