adbWireless is an app that allows ADB commands (Android Debug Bridge) over WiFi.
Running the app while your phone is connected to WiFi allows you to connect to your phone via ADB without the use of an USB cable. The app tells you what IP address to connect to from your comp by simply using the command "adb connect <ip address>" in command prompt/terminal.
ADB comes with the Android SDK, so you need to have this setup.
The app is only available for devices that's rooted, which a blog post to that here for HTC Desires.
adbWireless - Android Market