Good Gear Guide
In Pictures: Android tethering apps, 6 excellent o...
While not explicitly a Wi-Fi tethering app, Extended Controls ($0.99) is an excellent way to activate a Wi-Fi hotspot right from your phone's home screen, with or without an official plan in place. Extended Controls is a customizable power widget that lets you set up toggles for all sorts of phone functions.
In order to harness its hotspot-activating potential, you'll want to create a toggle with the "Hotspot Wi-Fi" function. Then you can just tap the toggle on your home screen to turn a hotspot on or off as you want or need to.
In Pictures: Android tethering apps, 6 excellent options