I have blogged previously about how to deploy an SSH-based VPN solution to offer remote control of corporate resources from 'untrusted' PCs safely (http://blog.brightpointuk.co.uk/deploying-ssh-based-vpn-solution). Should you need to, it is possible to access remote hosts from an Android device via VNC using a free SSH client and VNC viewer such as ConnectBot and AndroidVNC, both available from the Android Market.
To initiate the connection to the SSH server, download and install ConnectBot. When launched, you can enter in the details of the SSH server to be connected to:

Tapping on the Menu and selecting Edit allows you to edit port and username information:

When connecting to the SSH server for the first time, you will be prompted to acknowledge and save the server's public key and then enter in the password:

To configure port forwarding for the VNC connection, tap on the Menu button and select the option to Add Port Forward:

Set the source port to local, and enter in the IP address of the target machine to be controlled followed by the port used by the VNC application (5900 by default)

Now launch the VNC client and connect to the local IP address of the device (127.0.0.1) on the port number specified above as well as the password for the VNC connection:

After a few moments you will be connected to the remote machine:

Remote control-tastic!