use a male-to-male VGA cable you can get at any good computer store or radio shack. Typical lengths are 6 or 10 ft. I bought a 10 foot so I can sit in my favorite chair and do PC photo slideshows, surf the net, etc. It works great.
If you get a "no signal detected" msg this is likely the problem: your laptop likely will need a key combination pressed to display the info on your plasma (i.e, on my Compaq Presario the key combination is (Fn + F4) and I have to press the key combo 3 times to get the signal to display both on the laptop and on the panel.
Enjoy the immersion~