I am planning to do the same thing for my wood shop. I am tearing down three 100 yr. old barns and using the timbers. I bought two books that I feel have been excellent resources. The first is A Timber Framers Workshop by Steve Chapell. This gives a lot of engineering information in an easy-to-read format that will be very helpful. The second book is Building the Timberframe House by Tedd Benson. It is more of the practical hands-on information about how to put the frame together. I got them both from buy.com for a good price. There are several other books as well. Check your local library or bookstore, too.

Good Luck!