When you can barely make out the note you scribbled on the back of that coffee-stained receipt, and you haven't turned over the wall calendar's page since mid-2007, it's time to get organized with digital tools.

Nowadays the best place to find personal organizer software isn't necessarily on the desktop--it's on the Web. You already know that users are opting out of heavy desktop applications such as Microsoft Outlook for the likes of Gmail and Google Calendar.

But when it comes to managing your tasks, projects, and notes, the big names don't always have the best offerings. A new crop of rich Web applications offer smart tools you need to organize your life using any device that has a Web browser or an e-mail client, be it PC, Mac, or smart phone. As the founder of Lifehacker.com, I spend a lot of time trying out new Web-based personal organizers. Here are my choices of some of the best-of-breed options available online now.

1. Track Your Tasks With Remember the Milk

Remember the Milk--click for full-size image. The weekly status report is due every Thursday morning at 10:00 AM. You've got to pick up the dry cleaning next Wednesday after 3:00. Your business plan draft has festered unattended to for a week now. This afternoon it's your turn to pick up the kids from soccer practice. Before your brain blue-screens, take a moment to offload your to-do list into Remember the Milk, a full-featured task manager that categorizes and prioritizes to-do's into convenient lists.

RTM even makes "honey do" lists easy to manage: your Milk-using spouse, secretary, boss, or business partner can send task requests directly to your RTM inbox so you can incorporate them into your master plan instantly. If you upgrade to a Pro account for $25 per year, you'll have access to Windows Mobile syncing and an iPhone-friendly interface.

2. Store Notes and Research at Backpack

Backpack--click for full-size image. Collaborate on and manage notes and research with the Web-based notebook Backpack. Whether you're planning your next vacation, drafting The Great American Novel, or just want a private place to incubate ideas, you can create an editable page at Backpack and drop in notes, lists, news items, and comments.

Each Backpack page has a unique e-mail address, so when you're struck with a brilliant insight standing in line at the grocery store, just dash off an e-mail on your phone to insert it into your page on the spot. A limited free version of Backpack is available; pricing for paid versions starts at $12 a month and buys you file storage space, more pages, a group calendar, and message boards.

3. Get a (Virtual) Personal Assistant Named Sandy

Sandy virtual personal assistant--click for full-size image. Wake up to a cheery daily agenda from your new virtual personal assistant, Sandy, who communicates with you primarily via e-mail and text messages. Here's how it works: Send Sandy an e-mail that reads something like "Reminder: Lunch with Ted on Friday at 1PM." Sandy will add the appointment to Friday's agenda and fire off a reminder that afternoon with such good-natured aplomb you'll think she might be flesh and blood. Sandy can also store, tag, and recall important bits of information via e-mail commands, like a flight number or directions.