Panic Software makes, what has to be, the best ftp app for Mac OS X. The app is called Transmit.
Like most of the ‘best’ apps out there, this one isn’t free. But I gotta tell you after using Transmit for a few years now, I would pay $30 for this app all day long. The feel of the app is very consistent with the mac vibe, and for those of you that are used to browsing in Finder in List mode, they offer that too.
I don’t know much about Panic Software, apart from using their apps of course, but I love the fact that this product has been around for years, and the price hasn’t changed. It’s been 30 bones (well, $29.95) since I first discovered it.