JLP at AllFinancialmatters has a link to Harvey Mackay's 25 Lessons on Negotiating. They're all worth reading, but here are the ones I particularly liked:
3. The biggest tool in any negotiation is the willingness to get up and walk away from the table without a deal.Read the whole list here.
13. There is no such thing as a "final offer."
14. Try to let the other person speak first.
22. People don't plan to fail, they fail to plan. Top negotiators debrief themselves. They keep a book about themselves and their opponents. You never know when that information may be gold.
And my personal favorite is Mackay's Moral 25: When a person with money meets a person with experience, the person with the experience ends up with the money and the person with the money ends up with the experience.
I've figured out that far more things are negotiable than we'd ever imagine, and that negotiations take place all around us every day (at work, with customers, and with our families) without us even realizing it.
Although I've plugged it before, the absolute BEST book on negotiating I've ever read is Roger Dawson's Secrets of Power Negotiating. I particularly liked it because it has a "top down" approach to the topic -- it starts with an overview and some basic principles, and then goes into specifics.
And since it's now in paperback, it's cheap, too. And it'll pay you back many times over.