jCalendar
NOTE: This project has been superceded by the most excellent jQuery UI
jCalendar is an inline dynamic calendar built with jQuery. It originally started off based on the great jQuery date picker by Kelvin Luck but has quickly morphed into its own code base.
jCalendar v0.5 can be used with 3 form selects (one for day, month, and year) to visually select a specific date for input.
Coming soon will be v1.0, which will allow for not only visually selecting dates but also for displaying them in both mini and full page calendar views, similar to that of Google Calendar.