Backpack: Personal and small business information management.

Backpack's a fun combination wiki, weblog, to-do list and calendar that's featureful but not overwhelming. Make a page that contains check-offable lists, images, dated notes, and files about a project or idea. Link pages and share them with others for collaborative editing. Set up reminders that get sent to your email or mobile device about project deliverables - or to water the plants or pay the rent. Subscribe to page changes in your newsreader, and reminders in your calendar application.

For something more about it read the O'Reilly Radar post My favorite use of Backpack. (via Lifehacker and Micro Persuasion)