Well, there is no perfect solution for WLAN-Devices with various Linux distributions. However I did find a solution that seems to work pretty well with the Fedora distribution and the DWL-650+ WLAN Device. The only two drivers that I did find (and are working somehow) are madwifi and acx. The acx firmware/driver works only with a Kernel 2.6.10 and higher and doesn’t seem to be stable at all (also the installation is a little tricky). Sometimes I am able to connect to a network sometimes not and therefore it is not the solution I was looking for. The madwifi drivers on the other hand did work without flaws and installation was also quite easy (on fedora you need kernel-devel and sharutils). With a nice GUI you have not to deal with all the config-files and can easily set up your wireless network.
For further details see: http://www.hauke-m.de/w-lan/madwifi/