From the creators of Add to Contacts app now comes Calendar Search for WP7, an app that fills a lack of Windows Phone: the ability to search through the events calendar.
Through the application you can simply search using a keyword or extend the parameters by entering a range of dates on which specific account and choosing to do the research. Simple app has price tag of $0.99 and offers something that will probably come as an update for Windows Phone but that if it is useful for you, well worth the expense.
Calendar Search can be found here at Windows Phone Marketplace