Corte Madera and Larkspur are just a bit further North than Sausalito, Mill Valley and Tiburon, a 20 to 25 minute drive to San Francisco.  Therefore they are still referred to as being part of Southern Marin.   

Larkspur and Corte Madera share a school district, a police department and playing fields, so they are often referred to as  Marin's "Twin Cities". 

This area has a real hometown feel, with both a quaint old-fashioned little downtown area (the central part of Magnolia Avenue in Larkspur is on the National Historic Register) as well as a couple of larger shopping malls in Corte Madera: The Village and Corte Madera Town Center.  Larkspur & Corte Madera are very pedestrian friendly and bike-friendly.  In fact, the sidewalks, paved off-road multi-use recreational paths, and transit options make these ideal towns for those seeking a car-free life.

Larkspur & Corte Madera also offer great public schools in a well-run, small district (which is comprised of only 2 schools: Neil Cummins Elementary & Hall Middle School), ideal weather, and lots of recreational paths, parks, and programs.

There are a couple websites for commute options to the city or around Marin. 

http://www.goldengatetransit.org is the site for Golden Gate Transit's buses to the city AND the Larkspur ferry. 

www.marintransit.org shows the local bus lines and shuttles as well. 

http://www.mcbc.org is a good place to learn about bike routes and planned improvements. There are some great projects underway, linking Larkspur and San Rafael.