CoffeeCup Software offer at least three versions of their FTP client software as well as integrating it into other applications. They offer it as part of their free zip file manager, reviewed elsewhere. They offer a commercial version with enhanced facilities as well as their free client CoffeeCup Free FTP 4.2
Their free client has a simple interface and is easy to use. However, in my environment it proved no more reliable than Fire FTP, so was less attractive than the Firefox add-in because of the integrated nature of that solution.