This has been mentioned before but deserves it's own title for better searching.
(http://img505.imageshack.us/img505/9302/found0xm.jpg)
Here is a good PDF Framing manual you can print out for building reference. (Thanks to Glenn.)
http://www.awc.org/pdf/WCD1-300.pdf
PS - I just set up my printer for duplex printing, loaded it with good paper (so ink doesn't bleed through) and fired this up. Now I have a great little 55 page manual for the reference bookshelf!