After signing into Facebook, do the following:

1. Click on "Account" at the top-right of the screen.
2. Click "Application Settings"
3. Change the "Show" drop-down box to "Authorized." This will show all the applications you've ever given permission to.
4. In the resulting list, click the "X" button on the far right next to each app you want to remove to delete it.
5. On the pop-up box that appears, click "Remove" then click "Okay" on the next box confirming the app was deleted.

Repeat this process to remove all the apps you no longer use on a regular basis.

ReadWriteWeb explains that "doing this won't eliminate risk entirely - nothing can do that - but it's a good first step in reducing risk. However, as long as you have a Facebook account, your data won't be private. If true privacy is really a concern for you, it may be time to find that account delete button instead. (Hint: it's under "Account Settings.")"