A clear, printable map of the main trails inside Muir Woods can be found here.
You can find a printable map of the trails in Muir Woods and the surrounding areas in southwest Marin County by clicking here.
For history buffs, a map of the old railway route that ran from Mill Valley to Muir Woods and the summit of Mt. Tamalpais can be found here.
Below is the Google Maps map for the area's trails.