SSH and SCP (client and server) are built-in. This is what I use to get into my corporate network.

One thing that’s different under Mac OS X vs. and X11 environment is that your window manager isn’t the parent process of your terminals. So what? Well this makes it very difficult to run ssh-agent and have your keychain (of SSH identities) work the way you might be used to under X11.

I’ve been using SSH Keychain for a while now and really like it. Works with the OS X keychain and your identities.