My two favorite producers are Martha Stoumen, who I think makes extremely expressive but fun wines primarily sourced from Mendo, and Dani Rozman, who under his current project La Onda is doing incredible stuff in North Yuba with cab and Syrah. Frenchtown Farms, also in North Yuba, is doing incredible stuff up there as well, which is impressive considering how hard it is to farm there. They work with Gideon Beinstock, of Renaissance fame and currently making wine under the Clos Saron label.
Others include Jolie Laide (they sort operate with Martha out of Pax Mahle’s winery in Sebastopol, which has begun producing excellent Northern Rhône-style syrah in its own right), Stagiare, Minus Tide, Les Lunes, Stirm (great Riesling), Dunites (syrah), Augur (syrah), Idlewild (Italian varietals), Scar of the Sea, and Emme Wines.
They are all sort of the American reaction to the French glou glou scene, but much more balanced. Others have been around for a while of course, like Broc and Michael Cruse, but these shops have all gotten started up within the past five years or so.