Not specifically for programmers per-se, but the book "The First 90 Days" by Michael Watkins from Harvard Business Review was very valuable for me when switching to a new company when I was still in the corporate world. It's targeted at managers, but I find the situations translate to nearly anyone. It talks about making the right connections, working with your new boss, and so forth. Your first 90 days leave a lasting impression on your co-workers and manager, so it may be worth perusing.
Keep your mouth shut.<p>You're going to see things that they're doing that you think are stupid, with no possible justification. Don't say anything... yet. Give it time for you to learn whether or not there actually are decent reasons for what they're doing.