We are doing some of those, not to as large an audience as 37signals. One thing that makes it difficult is a lack of good tools to re-purpose content across blogs, wiki, web, print, presentations, animation/video, and PDF. We do workshops where we have the content both as a presentation (slides), a workbook/handout, and in a wiki. It's a lot of extra work right now. Conceptually we develop/refine in a wiki and deliver as presentation (PPT slides), print, and wiki (slimmed down, that is then available as an on-line notebook where further work can be done). I have contact info in my profile and would welcome any suggestions for tools that make it easy to develop and re-purpose content.