1. Send big files (YouSendIt): This service allows you to send files of sizes up to 100MB free. Email attachments have usually restrictions on file size.
2. Remote login for your home/Office computer (LogMeIn): This service allows you to remotely log in to your home/ office/ friends (of course with permission) computer from anywhere as long as you have access to internet.
3. Second life (anyone?): Go ahead, rediscover yourself.
4. Google Trends: See how the world is searching and Google Zeitgeist: Search patterns, trends, and surprises: see what the world is searching
5. Alexa.com: See where people are spending their online time.
6. Digg.com: Write your own news stories.
7. Reverse DNS Lookup (for spam): Once you find out who is spamming, contact their ISP or the company.
8. Location lookup with IP (Geobytes): Find out where a particular computer is in the world with a map. Use this Texas Tech IP 129.118.0.0 for demo.
9. Internet Archives - WayBack Machine: Find out how your favorite website looked 2 years ago or even 5 years ago.
10. Who-is Server: Find out who the website belongs to.
11. The Onion : News from a different perspective

12. Online Spreadsheets / word documents etc.

13. Google adsense