San Carlos / Belmont Mother's Club
- Support, education and friendship for local moms, and playgroups.
- http://www.scbmc.org/

Peninsula Builders Exchange
- A not for profit association serving Contractors, Designers and Owners in San Mateo County, California, since 1945.
- http://www.constructionplans.org/

San Carlos Tennis Club
- A tennis club for juniors, adults or teams. Includes playing fields and current standings.
- http://www.sancarlostennis.com/

San Carlos Chamber of Commerce
- Information and directory of member businesses.
- http://www.sancarloschamber.org/

San Carlos California AYSO
- San Carlos American Youth Soccer Organization. Includes schedules, volunteer information, contacts, playing fields and current standings.
- http://sancarlosayso.org/