TUIfly.com

 
Here's how it works

1. Select a flight
2. Click "Activate price alarm"
3. Enter your e-mail address
4. Each time the price of your selected flight changes, you will receive an e-mail.
5. You can deactivate the price alarm at any time.
Here's how your price alarm might look: Try it now

TUIfly.com price alarm - never miss another offer!

The price of your flight was reduced and you missed it? Now that will never happen to you again!
Simply save the routes you want and activate the price alarm right away. It will notify you immediately regarding price changes.

And to make sure you don't lose track of all the fantastic offers you can easily manage the flights you saved on your personal notepad with the price alarm or you can e-mail them or print them out.