Favorites, most listed by others:
North side of Palomares - just let 'er rip.
Mt. Diablo - too technical to just let 'er rip, but 10 miles of a lot of fun
South side of Morgan Territory - I do wish it was wider than a lane and a half, but the sight lines are good enough so you know when to expect traffic coiming up the hill at you, and the pavement is great
Mines Road towards Livermore
Del Valle Road heading back towards Livermore. Go as fast as you dare.
North end of Pinehurst from Skyline to the road to Moraga - very technical at the top, then you can just go on the flattish straightish part by the creek. A nice combination, and always pretty. Don't do it in the wet, though.
Pig Farm - either side. Not very long, but either side launches you into the land of gentle downhill with a bunch of momentum in your pocket
Eastbound on the new western extension of Dublin Blvd (access by going under I-580 from the Rowell Ranch rodeo grounds on Dublin Canyon/580 frontage road). Catch this one now, because the area is going to be built up in the next years and the traffic will ruin it. For now, brand new uber-smooth asphalt, very gentle turns (it's effectively straight) and very little traffic. It's two miles of major fun. There is one stop light and one stop sign. In both cases, you are going across the top of a T intersection, so if you are inclined to blow through them - not that I, as lawyer, advise such things . . . .
Wildcat Canyon, Tilden to San Pablo Dam Road - I've been down it so many times and know it so well, that I can overlook the less-than-perfect pavement. It's like a old pair of jeans to me, only more fun.
Faves in the Sierras:
The road from Crane Flat to Yosemite Valley. 10 miles of incredible down punctuated by some awe-inspiring scenery. Traffic can be a nuisance, but you'll be going plenty fast enough to take the lane and defend yourself adequately.
East side of Monitor Pass - only did it once, and then on a fully loaded touring rig, but what a descent and what a view.
Luther Pass, either side - who needs brakes on a road like this? Plus, the meadow at the saddle at the top is a nice little bonus
Mt Lassen, either side - Wheeeeeeeeeeeeeeee (breathe in) eeeeeeeeeeeeeeeeee. Good mix of technical and just flying.
Highway 88, eastbound, from where 89 comes in from Luther Pass to where 89 turns off to Markleeville. Coast or pedal, the choice is yours
Least favorites, also most listed by others:
Mt. Hamilton - jeez, does somebody go out there every week to make sure there are plenty of mini-potholes to fall into evey minute or so? And do they have to be so well disguised?
North side of Morgan Territory. If it isn't the worst pavement out there, it's on the short list. Okay to climb, absolutely craptastic to descend
East side of Old La Honda - You have to be nuts to take your chances on this one. Just go over to 84 and go down that.
Any major urban or suburban downhill - I hate wasting good downhills having to worry about when someone is going to back out of a driveway