I came upon this after investigating various sources. Here's what I use:
rdesktop -u USERNAME -d DOMAINNAME -p - -g 1680x1050 -a 24 -z -x 0x80 -D -r clipboard:PRIMARYCLIPBOARD -r sound:remote MACHINENAME
-x 0x80 will allow clear type tuning to work (see here) assuming you have Windows XP SP3, Vista or 7 as the server.
If you get a warning saying 24 bit color depth is not allowed, you will need to use the group policy edtor on the server machine to change the Administrative Templates -> Windows Components -> Terminal Services -> "Limit maximum color depth" setting. (see here)
I forgot to mention, on Windows XP, you will also need to add a DWORD value to your registry:
AllowFontAntiAlias with value
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp (source) and restart your machine.
The above also removed windows manager decorations and passes all keys (Ctrl+Alt+Del etc.) to the Windows machine. I have the resolution explicitly specified in place of using full screen mode on rdesktop to prevent it from taking over both monitors.