Does there exist a dashboard widget which displays my Outlook/Entourage and Exchange calendar?
There are no widgets for OSX for use with Outlook, there are calendar widgets for iCal or Google Calendars, that can be downloaded here but you will need to route all your calendars through iCal or Google calendars instead of Outlook and you probably won't want to do that.
Fantastical works with Outlook. http://flexibits.com/fantastical
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