just wondering if there is a way how to share calendars between Outlook 2007 & Thunderbird.
Have not tried it myself, but there is an ption in outlook to export calendars to ical or vcalendar formats. I think there would be options to import these formats in thunderbird also.
update: you will have to install an add-on 'lightning' in order to use this . guide here : http://www.ehow.com/how_7201355_import-outlook-calendar-using-thunderbird.html