You don't really say what you're really interested in, so here are some random thoughts...
Big Sur has some of the most amazing scenery you'll ever drive through. The highway goes right along the cliff for miles. It also has some great camp grounds and beaches. Don't miss Pfieffer beach or Andrew Molera. There's a lighthouse that's interesting to take a tour of if you time it right, if "ancient" technology interests you.
Santa Cruz - A beach front town still firmly stuck in the 60's. If that sounds interesting to you, you should stop.
San Francisco - Definitly. If you like citys san franciso will have something for you. It's all a matter of personal taste what you do...
http://www.grin.net/~mirthles/web/sanfrancisco_latest.html can be a good intro.
If you're camping while road tripping, the marin headlands is nice. I havn't been in years, but it's close to san francisco. Around there somewhere is the russian river, where I had a great time canoeing last summer with friends. The company hauls you up the river, give you a canoe and picks you up a day's ride down the river. B(lots of)YOB.
Portland is known for having the highest ratio of bookstores to people, so if you like that kind of thing...
If you're going to las vegas, you've almost made it to the grand canyon, so you might want to check it out.
In general, Highway 1 ("The PCH" if you're in southern california, but be warned that causes us nor. cal people to burst out laughing) is the senic route that goes right along the coast. You should plan your trip so that you spend some time on it, but not all of your trip, because it's very slow going.
Hope this helps,
Mathew