The integrated wireless card on most Centrino laptops is the Intel IPW2100 card. Actually, I believe it has to have that name to be considered "Centrino".
Anyways, there are two solutions to your problem. One solution is to use a driver wrapper. It takes the NDIS driver that is used in Windows and wraps the API to work in Linux. There are two projects that can do this: LinuxAnt DriverLoader and NDISWrapper. The LinuxAnt software is commercial, and I've never used it, so you're on your own. The NDISWrapper works pretty damn well, although it's far from perfect. It tends to "hiccup" at the beginning of connections some times, and it seems to dump a lot of warning/error messages about the driver being unhappy, but it only stopped functioning on me once after use for about a month. If you want to go that route check out
http://ndiswrapper.sf.net. You'll probably want the CVS version, it installs a hell of a lot easier than the old ones.
However, Intel recently released the GNU/Linux Centrino Wireless driver they've been promising. Go to
http://ipw2100.sf.net. Follow the directions on the website and in the INSTALL file in the archive. It's a bit hairy, but not too bad. You should be able to install it no problem. I haven't tested it much, but it seems to work very well with my Thinkpad T40.
Have fun!
EDIT: Trashed the URLs by accident. Oops.