Whatever you want to call it, Backpack is freakin' awesome. Backpack lets you create and share lists, photos, documents and more in a wiki-like editable Web site you can share - like this one. I am trying it out to share blog links with my client and I love it so far, though I wish it enabled RSS feeds for each page. I see lots of applications here for the PR community including instant press rooms that can be set up in the event of a crisis. Kudos to 37 Signals. It's also generating a ton of buzz. I bet they're going to give Jot and Socialtext a run for their money at least in the small biz market.