Here is some of software and scripts I have used.

Remote Control and remote desktop tools

Dameware Remote Control this is the most useful tool I have come accros as a sysadmin.

This Tool lets you connect to a remote computer very quickly and easily. No need for remote desktop top be enabled on the remote machine. Dameware uses its own protocol to connect to the remote host.

Dameware quick tips

• Connecting to a remote computer:
  
• Make sure windows firewall is switched off. Ask the remote user to switch the firewall off for you. If you can't connect using Dameware after using all of the tips, use the link below to enable remote desktop.
• Make sure you know the local administrator password, or of the user logged in.
• Setup Dameware to uninstall the service after you have finished. This helps with security of the system, as Dameware is notorious for its illegal usage.
• If you dont have the passwords for the remote machine, but you do have the server admin password, or an admin account, all is not lost. When connecting use the "domain" box. Ts will authenticate you against the domain controller, and grant you access.
• Connecting to a machine on another network over VPN is very easy, but you will most likely have to address the machine by ip, not hostname. Dameware is not good at getting a reliale name resolution

Remotely enable windows Remote desktop access
This is a page that show you how to remotely enable remote desktop top a PC. Ideal for remote diagnostics