After the success of Vista-like Ajax Calendar, dev.base86 has recently released Calender Eightysix. It is completely built from scratch with pure javascript, making use of some of the superb features the latest MooTools javascript framework has to offer.

Calender Eightysix is an unobtrusive developer friendly javascript calendar and datepicker offering a better user experience for date related functionalities. Calendar Eightysix has a variety of options to style and format the calendar to your needs. This is done by providing options while instantiating the class.

via An Unobtrusive Javascript Calendar & Datepicker | Web Resources | WebAppers.