Larus heermanni
Edited 08/23/11 - This is the second part of an original single gull post. I asked Don Roberson, creator of the amazing Creagus site, to confirm my IDs. He said, "Also, FWIW, the bottom gull is not a juvenile Heermann's Gull, which are extremely colorful with golden edges to all the back feathers, but is actually a first-summer bird (i.e., one year old... born summer 2010). We generally call those "first-cycle" now." Awesome, Don!
For other bloggers who have gull IDs, see John Rakestraw Birding in Oregon and beyond, Skev's B.L.O.G. from Leicestershire, and The Squirrelbasket from Wales.