What is the best remote desktop tool to connect to Windows from Ubuntu?

You can try remmina. While it uses the same backend as tsclient and friends (the backend being rdesktop). It has a more pleasing UI when compared to tsclient.

Ubuntu ships by default with tsclient. It works pretty well for me.

Try rdesktop

. A typical command looks like this

rdesktop 192.168.1.23 -k de -g 1500x1150  -r disk:mydisk=/home/soma

Parameters:

-k de............................ set keyboard layout
-g 1500x1........................ set resolution of the rdesktop window
-r disk:mydisk=/home/soma.........share your home directory with the remote machine