On Windows, I recently dumped Filezilla for the FTP function in Directory Opus---not a free program, but a powerful file manager replacement. I'd used Opus for years, but the FTP function didn't really work for me until version 10. Now it's awesome.
I basically have Opus running all the time---it's my file manager: a dual file lister and multiple tabs. FTP sites are just one more tab. Opus treats FTP sites like other folders on the file system, so you can drag and drop from any tab to an FTP folder. It's a bit hard to explain unless you see it, see the link below for screenshots and links to the demo on the official site.
You can also synch the local and remote folder, so when you drill down on one side, the other follows.
I have shortcuts to launch two of my top FTP sites. The shortcut opens two tab, one for local and one for remote.
For more, here's the section of my Opus tut about Opus FTP.