As Brian said:
According to a post on xda-developers, you can enable ADB over WiFi from the device with the commands
setprop service.adb.tcp.port 5555
stop adbd
start adbd
And you can disable it and return ADB to listening on USB with
setprop service.adb.tcp.port -1
stop adbd
start adbd
If you have USB access already, it is even easier to switch to using WiFi. From a command line on the computer that has the device connected via USB, issue the commands
adb tcpip 5555
adb connect 192.168.0.101:5555
To tell the ADB daemon return to listening over USB
adb usb
There are also several apps on the Android Market that automate this process.
It works.You just need to access the android shell and type those commands...
One other (easier) solution is on the Market: adbWireless, it will automatically set your phone.
Root is required! for both...