today i created calendar widget for plone.z3cform. its using mighty jquery datepicker plugin. for now i just made it functional, but there are some nice options i could include. well see it for your self. i hope i'll have some time to add test, add all functionality that archetype calendar widget has plus more.
did you notice jquery ui library (extension for jquery). it offers some useful stuff. maybe we should implement it into plone (as addon). any thoughts? ideas of implementation? did you use this jquery extension somewhere, your experiences?