I have a new favourite FTP/SCP client for Mac, in the form of MacFusion. It’s a GUI frontend for MacFUSE, which itself is a Mac port of FUSE, which allows non-native files systems to be mounted in user space, apparently.
What this basically means is that you can use MacFusion to mount FTP and SSH servers as if they were removable disks in Mac OS X, so you can browse them using Finder (or indeed any program) and drag and drop files on and off the server as if it were any other folder. You can even make it run at startup and have it mount the connections then, so they’re always available while your computer is turned on.
It’s not the easiest program to install – you have to install MacFUSE from Google first, which requires a restart, and then MacFusion – but once you’ve set some servers as your favourites the whole thing is very transparent. In future it should also support WebDAV and other file systems too.