With the IntelliGantt Web Part for Basecamp you have the ability to not only change Due Dates for Todo Items and Milestones, but also to give Todo Items a Duration by establishing a Start date as well. Furthermore, you can link any two Todo Items in a typical task dependency relationship by dragging from the predecessor Todo Item's Endpoint to the successor Todo Item's Startpoint.
We created a detailed forum entry to show you how it's down. For example, here is an image describing the task dependency feature:
Also, the IntelliGantt Web Part for Basecamp supports a 'Read Only' mode that may be useful when you wish to share project information but don't want folks to change things.
Read Only information is also covered in the forum.