I think the majoirty are voting FileZilla haha but yeah just stick with that and your good to go can add multiple sites, and its very easy to navigate
I used SmartFTP until they started to charge for it. That inspired me to try filezilla and I am much happier because of it.
Better you should use FileZilla FTP Client fot your Free Use, Its excellent performing. I have been using past 10+ monts there is no problem is uploading or downloading files from my website. Its absolutely free to use for personal. Lets try this ...
It looks like everyone already uses 'fireftp' Teaftp isn't bad either but I personally use WS_FTP Pro. You can find a torrent and download it in its full version.
FileZilla: Open source, most-frequently updated...thus, most stable and most secure. Quickest FTP client I've ever used...