As Murph notes, 101 is a large traffic sewer with homes, jobs and other commercial activity on either side. He has a comprehensive list, but I'll just quickly post a couple of videos and photos of the ones I've crossed. Directions given below are nominal, in that 101 is nominally north/south, but travelling north on 101 will actually take you quite a ways west. "West" is away from the Bay, "East" is towards the Bay, "North" is towards San Francisco and "South" is towards San Jose.
Westbound Willow Road crossing over 101. I stay in the straight through lane and out of the merge lane, though many cyclists choose to hug the curb (crossing merging traffic twice, but it's their funeral).
Westbound Willow @ 101 often looks like this, BTW, during the morning commute.
Here's a cyclist sharing the lane with a dump truck on Willow over 101.
Next is the Ringwood Avenue Pedestrian / Bike Bridge. This is a mile north of Willow and a somewhat nicer place to cross. Some residents on the west side of 101 want this access removed.
South of Willow a few miles in Palo Alto is the Oregon Expressway Bike Bridge. From the east side of 101 this bridge is pretty hidden and can be difficult to find if you don't know where it's at. I'll try to post video of this access later.
I planned to shoot video while crossing on University in Palo Alto this morning, but I had some technical difficulties, so maybe later this week. Are there any requests for other South Bay locations?