Each TUGboat issue contains a calendar of TeX and typograhy events. If you have an event you would like to have included, please send information to tugboat@tug.org.
For the online version, see the TeX calendar maintained by all TeX user groups: month view, year view.
Other typographic calendars:
On another front, we also have a printable 2008 calendar (letter-size PDF, A4 PDF, source) with images taken from the TeX Showcase. Many thanks to Gerben Wierda for maintaining the showcase, all its contributors, and David Tellet and Steve Peter for creating the calendar.