This is a great, easy to use, free app. If you have rooted your phone you can use this app to share your data/3G with other devices. The only downside is that this will be a big battery killer since its using the phones wifi and radios, but it does come in handy.
Go to your market and search for Barnacle
Then install it and open it
Before you start to use it go to settings and in the LAN section type athwlan0. Now the app will work properly
I use this app because its free, easy to use, and shows the info on the main screen. Good to have when you have limited data.