CrossFTP is a software that allows FTP and Amazon S3 client services, while CrossFTP Pro adds more services such as SFTP, FXP, WebDav, iDisk, Amazon Glacier and Google Storage. Key highlights are multi-tabs, threads, synchronization, scheduling, and more.

CrossFTP is packed full of useful features, including multiple tabs for local and remote file browsing, archives browsing, extraction and compression, and a CrossFTP Server startup solution for easy LAN file sharing. The software also includes Unicode support for international sites, a text and image quick viewer, recursive file transportations, and quick file filtering by marks.
Other features of CrossFTP include auto-reconnect and anti-idle functions, password protection, and cert management. There's even Bonjour (ZeroConf) service discovery and support for transfer compressing (Mode Z). CrossFTP Pro takes things even further, offering robust backup and bi-directional file synchronization, multi-thread queue processing engine, and secure encrypted FTP over TLS/SSL (FTPS) and SSH FTP Transfer Protocol (SFTP).
With CrossFTP Pro, you also have support for secure encrypted WebDav/HTTPS and MobileMe iDisk, Amazon S3, IPV6 support, and support for FXP (Site to Site) file transportation. Other features include download and upload speed limit control, a powerful search tool for remote FTP files, and remote quick view and edit. Finally, there's HTTP, FTP, and SOCK 4, 5 proxy support, and built-in scheduler support for the queue engine.
So, if you're looking for a powerful FTP and Amazon S3 client that ticks all the boxes, then CrossFTP and CrossFTP Pro are definitely worth considering.
Version 1.99.9: CrossFTP 1.99.9 is a minor update. It adds ap-east-1, eu-south-1, af-south-1, and me-south-1 regions for Amazon S3, and fixes that CrossFTP refuses to copy or delete files/paths with special character on S3.