What websites are similar to PatientsLikeMe?

http://www.onehealth.com/ an emerging site in this space.

Here is an academic answer to that question! http://www.jmir.org/2012/2/e46/ Crowdsourced Health Research Studies: An Important Emerging Complement to Clinical Trials in the Public Health Research Ecosystem (J Med Internet Res 2012;14(2):e46) doi:10.2196/jmir.1988

http://www.personasque.es (People who)  is a health community portal in Spain that was inspired by PatientsLikeMe (PLM). I would not say it is a "clone" of PLM, but it inspired by the same community principles of PatientsLikeMe.  Personas que was developed by the Publicis Healthcare Communications Group and is rolling out in different countries / languages.  (Disclaimer: I currently work for Razorfish Healthware which is affiliated with Personas que.)

I'm co-founder of a network of patient support sites for folks with rare conditions - http://bensfriends.org/. the real magic happens on the network sites though. click through on the homepage to them. If you want to check out patient testimonials, our blog has a ton: http://blog.bensfriends.org/

http://WhatNext.com is a new online cancer support network that instantly connects people to peers and resources based on a specific diagnosis. It was developed with participation from the American Cancer Society.

http://www.pulseofthepatient.com/ is a new website for social medicine. It focuses on cancer, but they plan on expanding to cover other diseases.

Try NHS Choices communities http://www.talk.nhs.uk - includes blogs and forums for patients and carers of conditions such as dementia, asthma, diabetes, mental illness and chronic kidney disease.

I have a curated list of patient community sites here that may be of some use: http://www.stumbleupon.com/stumbler/andrewspong/tag/patient-community/?grid

The Rare Genomics Institute http://www.raregenomics.org is a nonprofit that "recruits" patients suffering from rare disorders, connects them with genetics researchers, and crowd-funds their sequencing