Lifecrowd (social calendar)
This service is designed to help you meet people and participate in activities you've always wanted to try but never get around to doing, such as surfing, skydiving, wine tasting or learning how to paint. You can also add activities to your "life list" and receive notifications when a similar activity is happening near you. Sign-up is free, but most activities have a per-person fee. Event hosts can be almost anyone, so make sure you are comfortable with who is hosting your event before putting down good money. Lifecrowd is currently available in Chicago, Los Angeles, Orange County (California), San Diego and San Francisco.
Lifecrowd | Free and up