Google Flu Trends looks at what words people around the world are searching for and uses this aggregated data to estimate current flu activity in near real-time.

WebMD has a great First Aid & Emergencies section.  Includes when to call 911, and all steps are on one page.

http://symptomchecker.isabelhealthcare.com/home/main

• Natural language
• Different regions of the world
• Red flag indicators - seek treatment immediatly
• Common indicators

Comprehensive, well-researched information about health topics. 

http://www.nlm.nih.gov/medlineplus/healthtopics.html

Agency for Healthcare Research & Quality

This database was designed to organize evidence-based health information so that it can be printed out in advance and taken by patients to a medical appointment.

HealthLinkBC provides a comprehensive list of medical tests and how to prepare for them

Flickr Creative Commons User: Lab Science Career