Where do I find a Linux driver for my laptop's wireless card?

Okay. I went and gone and dunnit! Now that I’m fully on my new Win 7 desktop machine, I blew away XP on my laptop and installed Ubuntu 9.10. XP was so painful to use that I didn’t even bother to set up dual-boot—I blew it away completely. No regrets! Of course, there’s a few problems. Ubuntu can’t connect to my wireless network. I suspect it can’t see the built-in wireless card because the network light on the edge of the laptop won’t come on, even if I press the little button that turns it on and off (which was useful in XP when I wanted to isolate the machine from the network). It’s an HP Pavilion ZE4900. Any idea? Links?