Share-A-Ride matches carpoolers for free based on their destinations and other preferences.
Transitchek allows you to pay for your public transit pre-tax. You can save about $400 a year.
Looking to fly?
Kayak.com finds the lowest price by searching airline websites and discount websites for you.
Farecast.com helps you decide whether to buy now or wait for a better price. It uses historic data to predict whether a fare is likely to drop or not.
Yapta.com tracks prices for your flights. If the fare drops - Yapta will send you an email - even after you've bought your ticket.
What's great about that is many airlines will offer a refund or voucher if you can show the price of your airfare dropped after you bought it.