ChrisControl is a Portable RDP + VNC Remote Control Tool. It can be used to test if a remote system is running Virtual Network Computing or Remote Desktop Protocol services via a given Host Name or IP address.
Brynhildr formerly Zero Remote; is a free portable remote desktop program for Windows which includes both client and server in one package. This easy to use free remote desktop software allows you to remotely control another computer from a USB flash drive, on the go - no matter where you are.
TeamViewer Portable; is a popular all in one (server and client) Portable Remote Desktop Program. It can be used for desktop remote control and desktop sharing.