Online PIMs have gained in popularity of late and of all the ones I have checked out Backpack looks to be the most useful, at least for me. Backpack works a lot like Getting Things Done in that you keep all your items for a given project or major task and can easily follow up what you need to do next. Having your PIM information online means you can access it from any computer you might be using. The basic version of Backpack is free with additional storage options available for a fee. The coolest feature in Backpack is the ability to send you email and SMS reminders about important items.