To get wireless networking working via the GUI, use the ASU software which includes the campwifi.py script. It will connect to any open (unencrypted) network.
To connect to a WEP encrypted network, you'll need to SSH into your phone and issue the following commands:
ifconfig eth0 up iwconfig eth0 essid any iwconfig eth0 key 'mykey' iwconfig eth0 essid 'myssid' ifup eth0
Here are some applications available to aid in wifi administration..
lint-wifi work in progress
Mofi is software for the OpenMoko platform allowing phone users to search for and connect to wireless access points within range.