FORTUNE — Companies often tend to keep their biggest efforts internal, and they frequently start from scratch, with the idea that they ought to keep their plans close to the vest until the time comes for a splashy announcement. but more businesses should consider using the help and support of passionate outsiders.

Grassroots efforts can help a company find and connect with people who are already deeply involved in the topic and are often difficult to identify and reach by other means. for example, 23andMe, inc., a company working in the burgeoning field of personal genetics with financial backing from Google (GOOG), has built on the momentum established self-tracking healthcare movement to support its own business goals.

In 2009, the Michael J. Fox Foundation for Parkinson’s Research, the Parkinson’s Institute and Clinical Center, and 23andMe joined forces to discover who was most likely to get Parkinson’s disease. their goal was to get results faster by inviting the general public to participate in the study and to conduct much of the research online. they also wanted to help those who learned, through the study, that they had a higher chance of getting the disease to make smarter healthcare choices

To launch the 23andMe Parkinson’s initiative, the organizers publically invited anyone with Parkinson’s disease to participate. The first 10,000 to sign up online and agree to provide health and lifestyle information over the course of the study received their genomic “map” test for $25, instead of the standard $400 charge. in effect, the sponsoring groups were crowd-sourcing study subjects to get a larger sampling more quickly, using self-tracking methods for faster research results. these results could be used in conjunction with studies based on subjects making in-person visits with researchers.

One exciting outcome of the study was that participants formed tight-knit groups in the online community based on their common experience with Parkinson’s disease. for example, they were encouraged to take preventative actions based on their test results, and report their self-tracked findings online. The participants compared notes with each other while taking these preventative actions and asked experts questions in online discussion forums. The results of their accelerated learning were also tracked and made available to other participants.

The Parkinson’s research project was inspired by the energy and momentum of a broader grassroots initiative that grew out of a San Francisco Bay Area Meetup group called Quantified self. this loosely organized initiative hosts gatherings where members share their experiences related to topics as diverse as disease, mood, and cognition, among others. To record their findings, they use digital gadgets they design or computers, mobile phones, monitoring devices, or just pen and paper. By offering discounted genomic mapping and the opportunity to share results with others, the Parkinson’s initiative tapped into the enthusiasm and interests of this existing movement to help spread the word.

Alexandra Carmichael and her husband Daniel Reda, a former molecular biologist, joined Quantified self in San Francisco to learn how to track Carmichael’s long-term chronic pain and discover ways to improve her condition. soon after, they launched CureTogether, an online group where those with chronic pain could document and share the results of their self-tracking.

The community quickly expanded as people asked that their conditions be added to the ongoing group studies. Now, thousands of members share their own experiences of hundreds of health conditions. CureTogether is now collaborating on research with several universities. will Dampier at Drexel University’s Center for Integrated Bioinfomatics is using anonymized CureTogether data to build a treatment prediction system. When someone enters their symptoms into the system, it will predict (currently with about 80% accuracy) which treatments are likely to work best for them, based on what has worked well for other people with the same symptoms.

At the University of California Davis, April Armstrong and her team are comparing CureTogether’s skin disease data against published research to determine how representative CureTogether’s data is of the general population. this could help validate CureTogether as an accurate, trusted instrument for future research.

Quantified self now has groups around the world that are linked to each other through a shared website. It now includes a blog moderated by Carmichael and Wired magazine writers Kevin Kelly and Gary Wolf.

Along the way, members have created primers, videos, and guides for each other. this community, or ecosystem, brings together large numbers of diverse participants across many locations. It hosts meetings and conferences. Tim Ferriss, an active member of the original group, tapped members for feedback as he was conducting experiments for his book, The 4-Hour Body. Now, CureTogether and a firm that personalizes health information for individuals called HealthTap sponsor the Quantified self website.

The Quantified self grass-roots initiative provides a powerful example of a pack ecosystem. Pack ecosystems represent broad initiatives that are largely spontaneous, driven by a common passion among a group of participants without any clearly defined “center” to organize the efforts. some of the best known examples of pack ecosystems include extreme sports enthusiasts like big wave surfers, or “pro-am” (professional-amateur) initiatives that bring together people who have a passion for science, whether the participants are professionally trained or simply have an interest in the field.

These largely self-organized communities come together, driven by a desire to learn faster and improve. Participants connect with each other in person and online to share their experiences and challenges.

Because they lack clearly defined leadership and are so highly distributed, these communities can escape the radar screen of companies. nevertheless, they can provide powerful ways to connect with, and mobilize, deeply passionate participants who are highly motivated to support initiatives that align with their interests.

Companies ought to take advantage of existing pack ecosystems like the way 23andMe Parkinson’s initiative involved those in the Quantified self movement. Members tend to become highly connected, even well beyond the group and the larger movement. they can help spread the word about a company’s related projects and contribute their own expertise and passion.