When experimenting with different applications from the Android Market, you might come across a pop-up that asks if you want to set an application as your default choice. For instance, let's say you're trying out Google Voice on your phone and accidentally set it as the default texting app, but you want to be able to choose between Google Voice, Handcent and the default SMS app each time you send a text. Follow these steps to help correct the default app and get your choices back.
Step 1: From the Home screen, press the Menu button and then select Settings, and then Applications.
Step 2: Press Manage Applications and then find the application that was accidentally set as default (in this case, Google Voice).
Step 3: Press the Clear defaults button at the bottom.
The next time you go to perform the action you originally wanted a choice for, you will see the pop-up again. By not checking the box at the bottom of the pop-up, you will be prompted each time to make a choice between applications performing the same function.