Penguin Basics:
Penguin was founded in London in 1935 by Allen Lane, who wanted to make fiction more readily available to the public. Among the first authors he published were Ernest Hemingway, André Maurois, and Agatha Christie. Like Random House, Penguin has grown to become one of the largest English-language publishers in the world. As such, it encompasses a number of other publishing companies, including Viking, G. P. Putnam's Sons, Riverhead Books, Dutton, Berkley Books, and Puffin.
Fiction at Penguin:
Their website boasts of a "backlist of unparalleled breadth, depth, and quality," featuring names like Patricia Cornwell, Kurt Vonnegut, and Toni Morrison. With the the Penguin Classics line, their backlist is substantial.
From a writer's standpoint, this lucrative backlist is a very good thing: it gives editors the luxury of investing in new writers in a more traditional way. Most first-time novelists will not produce a bestselling novel their first time out the gate -- and maybe not the second, either. It's worth looking at a press that won't drop a writer when the first book or two aren't huge moneymakers.
How to Submit Work:
With a press of this size, your best bet is to get an agent. Few editors are going to read unagented manuscripts, or at least not on a regular basis. Learn how to find an agent or read about independent presses, who are more likely to read unsolicited manuscripts.