I have joined 6 different groups that are all based on walking and hiking. On occasion, we have gone out for breakfast or lunch after. I have met so many nice people through meetup and have discovered so many new canyons, lakes, vista points, I could go on. Now that I have a nice repor with so many different people, Its easy to find someone going to the beach, mountains, or desert in California, depending on which direction that day I want to walk/hike.
I also noticed a lot of people who have moved here from different countries or states utilize meetup for just this purpose. It's very cool to meet others from around the world!