Every time I click on a application, both Apple and third party applications refuse to open. The little blue dot appears below the app on the dock, and then it disappears. I've restarted the computer multiple times and no luck. It's a late 2008 MacBook. Any ideas?
You can fire up the /Applications/Utilities/Console.app and look over the logs as you are launching programs.
If the messages are not clear, you could either edit some details in the question or post a new question for each app / message that has you stumped as to a cause or solution.
Of course, you also might try some generic troubleshooting steps like rebooting, checking the apps with a new user, etc...