Lying across the Bay Bridge from San Francisco, the East Bay consists primarily of Contra Costa County and Alameda County. It has a unique culture that's more laid back and uncomplicated than its Western neighbors.
Oakland, the area's largest city, is famous for its somewhat smaller Chinatown and its beautiful waterfront Jack London Square , as well as its large port and eucalyptus-spotted hills. Berkeley, just north of Oakland, is home to the University of California  and tens of thousands of students, as well as left-leaning politics and great food.
What the locals call "the East Bay" is really two fairly distinct regions separated by the East Bay hills. On the bay side of the hills in the west, the cities of Berkeley, Oakland, San Leandro and Hayward rise from the edge of the San Francisco Bay up the western face of the foothills. The climate tends to be temperate, the culture diverse and the traffic horrendous.
On the eastern side of the hills, the towns of Walnut Creek, Pleasanton and Livermore lie in the area known as the Tri-Valley region (named for the Livermore, San Ramon and Amador valleys). The climate here is more like that of the San Joaquin Valley, with foggy winters and scorching summers. The population is more homogeneous, but the traffic is still pretty awful. Originally, when the small towns of the Tri-Valley area began to grow into immense suburbs in the 1970's, many people commuted over the hills to work in the South Bay, the Peninsula or the City. Today, many large corporations have offices in the Tri-Valley area, and the suburbs of Pleasanton and Walnut Creek are growing into small cities.
However, due to the population exodus from "The City" (due to $$$ high prices and low bang for the buck) and the movement of some families from the west side of the hills it is growing very rapidly and the traffic is now as terrible as any place in Northern California. As the locals would say "The traffic is like, um like, hella bad here"
Contra Costa County in itself is divided into three parts simply referred to as: "West County" near Richmond, "Central County" for the booming area near Walnut Creek, Concord, and Mount Diablo, "East County" for the area near the Delta which includes Antioch or Brentwood.
The two main area codes are (510) for Western Alameda county and the "West County" region of Contra Costa, and (925) for central and east Contra Costa County and for the central eastern part of Alameda county near the fairgrounds Pleasanton and Livermore.
There are many malls and shopping centers in the east bay. Sunvalley Mall (Concord), Stoneridge Mall (Pleasanton), Bay Fair Mall, New Park Mall, Southland Mall, and Hilltop Mall are some of the largest.
There are three professional sports teams in Oakland: Oakland A's (baseball), Oakland Raiders (football), and the Golden State Warriors (basketball).
The University of California Berkeley  is world renowned for it's educational standards and its liberal viewpoint of most things. The California Bears Football team plays in ancient memorial stadium, which sits right over the Hayward Faultline.
There is a Cal State school in Hayward (CSU East Bay  - formerly known as "CSU Hayward"). There are many two year junior colleges here but one of the biggest is Diablo Valley College , located in Pleasant Hill, CA Contra Costa County
The East Bay Regional Park District  maintains 65 parks across the East Bay, ranging from easy access picnic areas to off-limits wildlife sanctuaries. More than a dozen campsites range from "family camping" to backpack areas.
East Bay fans love sports; you can see pro teams in Oakland, across the bay in San Francisco and in the south bay (San Jose). The CAL Bears play at UC Berkeley .
Zachary's pizza in Berkeley, Oakland, and San Ramon. A local and regional favorite with notoriously long lines. Pizza like you dream about. Available in deep-dish or regular. Best deep dish pizza this side of Chicago!