Turning the data connection on and off takes 7 clicks on my device, and I like leaving it off most of the time but retaining manual control over the status. So, I wanted a button on the home screen I could use to turn it on or off (and have the label and icon both change accordingly to make it clear what the status is). Note that if you do turn 3G on or off elsewhere (rather than by clicking the button) the label and icon will be out of sync. It wouldn't be too hard to update it to check the network status, but I only ever turn it on or off with this button so I didn't bother.
Download the three files below, and import them to your device. To add the button to your home screen, long-press on an empty spot on your home screen and select Widget. Select Task (with the Tasker icon). On the tasker screen, select the 3G_Toggle task. Hit the green checkmark to save your new widget. Note that I have the widget use a hippo icon when 3G is on, because I find that adorable and amusing. Feel free to change the widget icon to whatever you like (it's step 6 within the 3G task that determines it).