Smarter Living Airfare Update
Recieve email info on all the cyberfares available for a specified city of departure. All they ask for is your email address. They also have an airfare auction called Sky Auction.

Travelocity Farewatcher Email
They will email you the lowest fares and cyber fares on any route you specify. You have to register as a free member.

Trip.com - Deals - 2 - You - Low Fare Notification
Emails lowest fares for specified routes. Also has a free newsletter with tips and specials. All they ask for is a name and an email address. No privacy invading registration, no password to remember.