Ran across a couple of resources for sizing beams and joists while working on a remodeling project on the family barn. I figured I'd share as they've been pretty useful for me.
http://www.southernpine.com/publications/ (http://www.southernpine.com/publications/) The Southern Forest Product Association has published span tables for southern pine. These appear to be have been updated to reflect the new design values from last year. I used both the joists/rafters doc as well as the headers and beams when I first started figuring out how to structure my changes to the barn.
http://www.woodbywy.com/software/forte-software/ (http://www.woodbywy.com/software/forte-software/) Weyerhaeuser has released free software for wood member sizing. This is primarily oriented around their in-house products. However, you can size a couple of species of dimensional lumber as well. There is something of a learning curve here, but I watched a couple of their tutorials and was able to get up and running pretty quickly. The nice thing about their software is that I was able to check some odd spans not covered in the normal span tables and do some sizing involving point loads.
Enjoy!