I'm not a huge fan of the ASP.Net Calendar control, for the simple reason that it adds another step to any page you load it onto. Users would just as soon type in the date instead of clicking on the calendar, selecting the date, and returning to the previous page. So I found this free popup calendar control for ASP.Net and ASP.Net 2.0.
Here's a link to the control's website. It was fairly simple to install and start using, as well as extremely customizable.
Show a Popup Calendar, Disable Holidays and Weekends Selection, Move the Calendar (IE Only), Use fade Effects, Draw a Shadow, Keep Over the Select Options and Applets, Select using ranges of days (Specific Date, Today or Another TextBox Field), Use the Culture for support the calendar language, Support Right-to-Left Document for next cultures: Arabic, Farsi, Urdu, Hebrew and Syriac. Use different formats like (dd-mm-yyyy, yyyy.mmmm.dd, mmm/dd/yyyy, etc.), Use CSS to change the appearance of the Calendar, Support Required Date, Implementing IntelliSense Support (HTML), Validate dates using the keyboard, Examples in (VB.Net and C#), Run in (Opera 7.21+, Netscapte 7+, Mozilla 1.4+, Mozilla FirexFox And IE5.5+)