My apologies. Even though I was able to get rdesktop to compile and run, it was unusable because the keyboard mapping is completely wrong. I had found a working copy of it, but it was a part of some sort of VNC application. I lost track of where I got the app from and where I installed it to...
Nice! It compiles without errors once that flag is added. I also had to change the compiler in the makefile to point to /usr/bin/cc. make wasn't able to find cc without an explicit path for some reason (even though /usr/bin was in my path.)
So, now all I need is a VPN client!
On a side...
I just tried the same thing using XP Pro. It's embarassingly fast compared to OS X. Apple definitely has to work on speeding up iDisk access under OS X. It's unbearably slow to access an iDisk using the Finder.