Whipple Well offers one of the most complete online databases of California Place Names I've found so far. They currently include 1173 place names for Santa Clara County:

Place names beginning with Aa - KS
Place names beginning with KS - So
Place names beginning with So - Zz

When looking for a particular place, you may want to review these county boundary comparison maps, also on the Whipple Well site.

1850 and 2001 County Boundaries - comparison map.
The Changing Counties - how county boundaries have changed over the years.

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Other sources for Place Names in Santa Clara County include:
Geographic Names information System - USGS
US Gazetteer - 1990 Census Bureau populated places
Place Names in Santa Clara County - sfgenealogy.com
Santa Clara Co. Cities and Towns - HomeTownLocator
Santa Clara Co. Communities List - ePodunk
Silicon Valley Cities and Counties - Silicon Valley Online