We've just enhanced the IntelliGantt Web Part for Basecamp to support viewing all the milestones, todo lists and todo items from the projects of your choice. You can select a single project, multiple projects or all projects. We've tested the IntelliGantt Web Part for Basecamp with thousands of items and it scales very well, providing you a great user experience now and in the future as your projects grow.
Furthermore, we've created several ways to view your Basecamp items--
1) A Default view that shows everything
2) A My Todos view that shows only todo items assign to you
3) A Milestones view that shows only milestones
4) A Resources view that groups all milestones and todo items by assignments.
And, of course, this is all done across as many Basecamp projects as you'd like.
Here's a screenshot of the Resources view.
You can try it yourself today and see what you think.