Best stops en route to Los Angeles?

I would try to hit the wineries in Paso Robles. Most places have tables and you can sit and have a picnic and do a little wine tasting. 

I just went in April with some girlfriends and we went to the Brecon Estate which was fantastic if crowded. I would also try Bianchi Winery and Tasting Room and a place called Pasolivo Olive Oil which is an olive oil manufacturing place. I know it seems weird to tell you to go to an olive oil store but I promise, it's worth it. I bought a jar of truffle salt there and it's the best thing I've ever purchased in my life. 

I would also stop at San Luis Obispo. I don't know it well but it's a great little town. My friends and I had lunch at a place called Novo Restaurant & Lounge and it was fabulous. Adorable little outdoor patio area and they serve amazing bacon Bloody Marys. 

Have a blast!

These aren't really off the 101, but the best stops on the way are Hearst Castle, Big Sur, Carmel, Santa Barbara and Neptune's Net. :)

If you have some time to break off the 101, Monterey or Santa Cruz are fun spots, though Monterey is more on the touristy side. Santa Cruz is really the most proper surf town in Northern California in my opinion. As Courtney mentioned, wine tasting in Paso Robles. There's a cool winery there that also makes their own spirits, Villicana Winery. And Firestone Walker Brewing Company is one of the best breweries in California. 

San Luis Obispo can be touristy, but it's a fun and charming town. For a quick hike with a great view, there's Bishop Peak, and Central Coast Brewing is a great local brewery. Santa Barbara will be the busiest town you drive through, but it's fun. Lots of great taco shops, like Lilly's Taqueria, and for an awesome view overlooking the ocean from the hills, head up to the Chumash Painted Cave. The cave itself isn't necessary worth the visit, but the view on the way up there is epic. 

Sorry this is a tad late, hopefully you're still on the road or get to stop on some places on your way home! I live smack dab in the middle of SF and LA, so I'll highlight my local faves. 

Big Sur Bakery and Restaurant in - you guessed it - Big Sur, is supposed to be incredible, I've heard rave reviews from several friends and family members and my mom enjoys cooking from their book. The scenery is also breathtaking from photos, though I've never hung out there myself. 

Madonna Inn Resort & Spa in SLO is kitschy PINK heaven, if you're in to that kind of think (I am ;)). My favorite restaurant in SLO is Goshi Japanese Restaurant, but Novo Restaurant & Lounge that someone else mentioned does have a lovely atmosphere. A similar restaurant to Novo is Luna Red - their food is more creative, but hit and miss for being truly incredible, in my opinion. SLO also has The Habit Burger Grill (one of several locations on the Central Coast) which is one of the very best burger chains, in my opinion (native to Santa Barbara). Make sure to try the mocha malt! 

I think the botanical gardens at California Polytechnic State University, San Luis Obispo are a hidden gem of the Central Coast, and the Bob Jones Trail is a lovely (very easy) walk from the best ice cream (get the oatmeal raisin flavor!) at Avila Valley Barn to the beach. There's a little deli half way through the walk that has remarkably good potato salad. 

If it's not too hot, the hot tubs under the trees at Sycamore Mineral Springs Resort are great. 

The best things in Buelton/Solvang are an orange julius and whatever goodness is on the menu at Industrial Eats and pastries from Mortensen's Danish Bakery. 

My favorite haunts in Santa Barbara are the marvelously hidden tiki bar meets speakeasy, The Imperial, and the designer consignment shop Renaissance Fine Consignment. 

Have a wonderful trip! 

Take Highway 41 all the way to US 1 (Pacific Coast Hwy). It will put you next to San Luis Obispo. One note of caution, this detour will add about 2 hours to your time down to LA, but it's well worth it. If you can spend the night in San Luis Obispo even better. The rest of the way down to LA is by US 1 or 101, and that will take you through Santa Barbara.