Valve's Handbook for New Employees is online for all to see. I love reading stuff like this and the Zappos Culture Book. It's a fascinating peek into how the organization is run and how newcomers are indoctrinated into their culture.
"Hiring well is the most important thing in the universe," according to the Valve handbook, and I agree. Individual employees will make or break your company. You had better be deadly serious about who you invite to join the club, and how they are treated once inside.
Like most people who have to work for a living, I spend more waking hours at my office than anywhere else, so it makes sense to invest in that environment. That's why I created our company's Culture Book last year. I'm really interested in this stuff!