I plan to publish next week the script to include HTML in SharePoint calendars. I am giving myself another week to clean up the code and complete the validation.
Update [11/16/2008]: the script is now available here.
As an example, the above picture is a month view of the printable progress bars (the date for each task is the due date).
If you are already using the “HTML calculated column” and have a test list, I’ll be happy to send you the code for testing purposes. Feel free to contact me by e-mail at Christophe@PathToSharePoint.com.
All these customizations are done through the standard SharePoint UI, they don’t require SharePoint Designer or any other tool.