Joke411 is a free "joke of the day" kind of application. It loads during the Système startup and displays a daily joke in a balloon message near the Système clock.
Joke411 is fully customizable: you may add your own set of daily jokes by simply editing a text file that contains all jokes. You need to edit "joke.txt" in a text editor in order to customize the displayed jokes.
To install, unzip application and add a shortcut to Windows Startup menu. To uninstall, simply remove the shortcut and delete joke.exe and joke.txt from where you unpacked it.
Joke411 is free. It does not include any kind of adware or spyware.