Some days ago I spent some time getting a PCI WiFi 802.11G network card to work in CentOS 5.4. My card identifies itself as a “D-Link System Inc AirPlus G DWL-G510″ (PCI id 1186:3c09) and uses the “RaLink RT2561/RT61 rev B 802.11g” chipset (PCI id 1814:0302)
A driver for this card is included in the standard CentOS 5 kernel (tested with kernel-2.6.18-164.9.1.el5) under the name rt61pci, however to be able to function a binary firmware is needed. Some searching revealed that the firmware is available in Fedora’s rt61pci-firmware package. I rebuilt the package and put it in my CentOS playground repository.
So, if you have such a card and want to make it work in CentOS5 you might want to try running rpm -ivh http://rpm.resare.com/centos5-playground/i386/rt61pci-firmware-1.2-6.el5.noarch.rpm as root. Once that is done, running modprobe rt61pci should do the trick.