BackPack is a fascinating little product. It's basically a structured wiki for non-technical users. But, the killer feature for me is the reminders. Oh, I think it will have an impact on my day to day stuff. Web geeks will note that you can easily set up a similar system with a good blog and wiki. It's obvious the Signals are aiming for a wider audience. Just like with Basecamp and blogs, they are infiltrating the mainstream with wikis, and people don't even know it!