Simply the best ftp client on Mac OS X: Transmit.
A next-generation FTP and SFTP client for Mac OS X. With its famously clean drag and drop interface, and powerful features set, Transmit makes maintaining files and folders through the Internet as easy as, well, the Mac!
Amazon S3 Support
Manage your simple storage service, Mac-style
Copy and Preview Remote Web URLs
Select a remote item, hit copy: instant URL!
iDisk / WebDAV
Get files on your iDisk, faster than the Finder!
Edit in Whatever
Edit any remote file, in any app — even graphics
Run tests, save reports, and have more control
Upload faster than ever. See it in action!
..and much more!