FireFTP is a simple but powerful add-on that gives you an FTP client within Firefox.
FireFTP does a surprisingly good job of transferring files and even features advanced options such as directory comparison, syncing directories while navigating, SFTP, SSL encryption, search/filtering, integrity checks, remote editing, drag & drop, file hashing, and more.
You can save profiles so that you can connect to as many servers as you want which saves a lot of time when it comes to regular connections. A statusbar keeps you informed exactly how long a transfer is taking and the file manager is exactly the same as Windows Explorer. The only problem we found is that some connections are dropped.
FireFTP is a surprisingly powerful FTP client that enables you to perform all of your FTP tasks within Firefox.