Sometimes it seems like your phone has a mind of its own. You tap on a link and it opens a screen in the IMDB app when you wanted to view it in your browser. You want to edit a Word document in QuickOffice but it opens in the viewer-only version of Documents to Go. If you don't like the app that app that opens a particular file type, simply navigate to the App Settings menu, select the Program you want to unassociated and tap Clear Defaults.
The next time you try to open that file type, you'll be prompted to choose a new default app.