Well, this is something I know a lot of Haiku users have been wanting for a very long time, and is something Haikuware has tried to support from the start (1, 2, 3)! Through rev. 42775, Michael has added the ported wpa_supplicant to Haiku, and describes that it is working on a limited set of hardware working on the hardware Michael had at his disposal to test on (ideally, it should work with all wireless adapters Haiku has a FreeBSD based driver for) - one can now join WEP/WPA/WPA2 networks on Haiku; finally!

Seems as though the dividends of Michael's long term contract with Haiku are already (he just started) paying off (as we knew they would of course :) These are preliminary commits, with inevitably much more work to come in the future to get it stable. 

Add the wpa_supplicant optional package. It should be stable and is working onthe limited set of hardware I could test it with.
By installing the wpa_supplicant one can now join WEP/WPA/WPA2 networks by either selecting them in the network prefs/network status applet or using:"ifconfig join [password]"The wpa_supplicant opens a dialog asking for more details if it can't connect with the given information.
Note that there is no way to automatically store that extra info right now, soit has to be provided on each join. The configuration can however be stored manually into the /boot/common/settings/network/wireless_networks config file.