cPanel has its own File Manager but any web based file transfer/managing utility isn't going to work as well as one that runs on your computer.
FileZilla is a free ftp client that is reliable and stable. You can download it at:
You can use the one Todd uses and get either the free version or paid version. i use the paid version.
CoffeeCup Direct FTP
For those needing something with a little more power, Chris uses and recommend IpSwitch WS FTP Pro. It's quick, stable, and reliable.