I just took a trip to Pinnacles National Park yesterday and it was AWESOME.
It's located near Hollister, CA.
I'd hardly ever heard of it (and I like to think I know my NPs...)
It's small, and not on a usual route to anything. It's actually best to visit in the _anytime but summer_. The hiking was nice, really nice. They even have trails that go through talus caves. This is what my username comes from, so yeah, I nerded out a little.
The rock formations are neat. They have climbing routes that are marked and trails that show you how to get to them.
It was $15 for the day or $25 for a year. We live less than 3 hours so I went ahead and bought the year (we will definitely be back at least once).
Anyway, we had such a blast. I wanted other people near central CA to know about it. But only cool people like mustachians (I kid, I kid).
Also I thought people might chime in with parks near them (national, state, or otherwise) that are lesser known but worth the trip.
Side note: When I look for fun things to do nearby, I feel like everything really starts up in April. Going to Sacramento in April to see the railroad museum. Visiting the cave at our old job in April. Tours that don't happen on weekdays until April. I was really happy to find something that is outdoors and great to visit before April!