If you are PC user, you will feel frustrating that you cannot charge your iPad through the PC's USB. I've thought that it is the hardware limitation of PC, but I was wrong. After install this ASUS ai charger:

http://event.asus.com/mb/2010/ai_charger/

You can now charge your iPad using the USB port of your PC. The software even claim it will charge iPhone and Ipod Touch faster that I didn't test. The software is not limited to ASUS motherboard, I successfully installed and used on my Foxconn motherboard without any problem.

After installed the software, you will see a new icon is shown on the system tray. A red cross means that the USB port is not charging.

When you plug in your iPad, it will install a new device driver and the icon will change. Now you can see your iPad is charging!