As I surf the internet, below are some sites that I have found to be interesting and/or useful … in no particular order.
Let me know if there are any dead links.

Reference
http://www.refdesk.com/ – an online library is one click away
http://www.bartleby.com/ – another amazing online reference library
http://www.highbeam.com/ – access to more than 3000 news/scientific/medical publications (requires subscription)
http://www.reporter.org/desktop/- “Reporter’s Desktop” has multiple links to help you find information about people and subjects
http://zipskinny.com/ – view your zip code’s census data and compare it with other zip codes
http://www.zillow.com/ – free online estimate of your (and your neighbor’s) home value
http://www.trulia.com/ – online real estate search similar to Realtor.com with demographic data, price, and popularity estimates
http://www.allmyfaves.com/ – visual collection of favorite internet links

Medical
http://www.emedicine.com/ – database of free medical information
Gray’s Anatomy – pictures and descriptions of human anatomy
http://www.visiblebody.com/ – interactive human anatomy including “over 1700 anatomical structures”
The Merck Manual – free access to a library of medical texts
http://www.mdconsult.com/ – full text from several hundred medical books and journals (requires subscription)
http://www.diagnosispro.com – free program that creates a differential diagnosis based on symptoms entered
http://www.modernmedicine.com/ – contents of multiple medical magazines contained at one site
http://www.hospitalcompare.hhs.gov – compare national “quality indicators” for each hospital
http://www.netdoc.com/hospital-rankings/ – another site to compare hospital quality
https://catalog.ama-assn.org/Catalog/cpt/cpt_search.jsp – see how much Medicare pays physicians for management of a specific medical problem
http://www.statehealthfacts.org – a wealth of data on demographics, costs, and payments
http://www.livescience.com/ – very cool site with lots of interesting articles on science and health
http://www.acsh.org/ (The American Council on Science and Health) – debunking medical myths left and right

Computer-related
http://www.xtort.net – large list of freeware computer utilities
http://www.adrive.com/ – 50 GB of free online storage and backup
http://mozy.com/ – 2 GB of encrypted and automated online backup
http://www.comodo.com/products/free_products.html – free antivirus, firewall, rootkit detector, and other software
Lifehacker Guide to Freeware Apps

Utilities
http://zoho.com – free online office suite similar to Microsoft Office
http://www.openoffice.org/ – free downloadable office suite similar to Microsoft Office

Miscellaneous
http://anonymouse.org/anonwww.html – surf the web anonymously
http://proxy.org/cgi_proxies.shtml – more sites from which you can surf the web anonymously
http://www.spoofcard.com – subscribe to this service and change the caller ID information on calls that you make
http://flightaware.com/ – track airline flights and see the real-time flight path
http://www.sidestep.com/ – free comparison of travel values across multiple sources
http://www.snopes.com/ – the ultimate site to debunk those urban legends