Conky's man page says,
Conky is a system monitor for X originally based on the torsmo code. Since it's original conception, Conky has changed a fair bit from it's predecessor. Conky can display just about anything, either on your root desktop or in it's own window. Conky has many built-in objects, as well as the ability to execute programs and scripts, then display the output from stdout.
Apart from system variables, I've configured conky to display fortune cookie and random jokes from jokes4all.net (via RSS). Wrote a program to display RSS data in plane text. You can find it here. It's in php.
My ~/.conkyrc file is here.
My desktop looks like this..