By way of ModernHiker, the Santa Monica Mountains National Recreation Area web site has a very useful new tool for some of us more casual hikers: a Flower Finder.
See a flower you don't recognize while hiking? Go to the SMMNRA site and scroll down to the Site Searching section for the Flower Finder and the Compact Flower Finder which has a lot less notes. Answer the questions and it will lead you through describing your unknown flora until it is properly ID'd.
Add this to our favorite native plant database over at the Theodore Payne Foundation and you've got a lot of stuff covered.