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1. Tidy your to-do list

Ditch the Post-its and sign up for a free account at RememberTheMilk.com. Its simple interface lets you list all your tasks along with a priority level. The site will then send you reminders—"carpool to YMCA at 4 P.M.!"—via e-mail, IM, or text message.

2. Plan a trip

With TripIt.com, you'll never riffle through pages of confirmation e-mails at the airport check-in, car rental counter, or hotel shuttle pickup again. Forward your travel confirmations from various Web sites to plans@tripit.com, and the site will consolidate it all into a day-by-day itinerary, plucking out the essential details and adding maps, directions, and local weather forecasts.

3. Never miss a birthday

Register at JackCards.com and enter birthdays for your friends and family, then select a card for each one. As their big day approaches, Jack Cards mails you a card (prices start at $2.50). Just stamp and send.

4. Track your work contacts

You don't just enter names and phone numbers at HighRiseHq.com. You can also include identifying information, like whether you've met in person or which projects you've collaborated on. You can even jot notes about your last phone conversation and check a box if you need to follow up (you'll get an e-mail or text reminder). Invite your colleagues to join, and you can collaborate and share information via the site.

Organize everything: Expert advice on taking charge of your clutter