If you’re up at this late hour, you might want to take advantage of Continental’s IAD-SFO r/t fare for $105-115 including taxes–this deal will probably be gone by morning.
Codeshares on United available if you route through Chicago or Denver. For maximum mileage, route through Newark.
The rate is good for some dates in December and from the second week in January through EOS (end of schedule). Book it at continental.com.
I’ve never seen a transcon fare this cheap!