In the crowded field of online health, these networks or websites attracted more unique visitors than the rest, according to comScore data from December. 
1. Everyday Health has pulled away from the competition for unique visitors, following its merger with Revolution Health and content designed to bring visitors back on a daily basis.
2. In December, iconic health brand WebMD scored a partnership with FDA for drug alerts and other consumer updates, the first of its kind in the space. WebMD’s Medscape Physician Connect is one of the largest physician social networks online.
3. AOL Health announced plans to join the Healthline Network (#9) in January, so watch for Healthline’s unique visitor count to jump ahead of competitors in the coming months.
4. Last October, Yahoo! Health inked a deal with Everyday Health for the provision of content from several Everyday Health Network sites. Yahoo climbed from 6th to 4th place since December, by comScore’s visitor count.
5. About.com Health launched an online social dieting network last October – nutrition and diet information tends to attract large audiences – but was bested by Yahoo Health in unique visitor count since then. 
6. Many consumers view the NIH website as a gold standard for trustworthy content. In addition to consumer health information, the site contains links to government-funded research as well as ongoing clinical trials, and is completely free of advertising.
7. MSN Health & Fitness fell from 5th to 7th since October, despite offering consumers several interactive tools such as customized workout programs and an “ask the experts” feature, where doctors respond to consumer-submitted questions.
8. QualityHealth‘s scheduled $50 million merger with WebMD fell through in November, though WebMD did acquire a minority interest in the company. WebMD also entered into an advertising agreement whereby the two companies will share media inventory.
9. Healthline added AOL Health, dLife, iVillage, Organized Wisdom, tudiebetes.com and WrongDiagnosis.com to its network in January. According to Joe Petrosino, VP of sales, Healthline has already surpassed all of its 2008 ad revenue billings in 1Q of 2009.
10. Healthgrades provides consumers with ratings, profiles and cost information about 5,000 hospitals, 16,000 nursing homes and roughly 650,000 physicians. The service also allows physicians to educate patients about their specialties and practice.