From member Abbynrml (http://countryplans.com/smf/index.php?action=profile;u=3563)
http://www.engineersedge.com/commercial_lumber_sizes.htm (http://www.engineersedge.com/commercial_lumber_sizes.htm)
Keep in mind that hardwoods use a sightly different method of sizing. The above link would be for common construction lumber.
Hardwood and softwood list...
http://www.woodbin.com/ref/wood/lum_dimensions.htm (http://www.woodbin.com/ref/wood/lum_dimensions.htm)
also info at Wikipedia...
http://en.wikipedia.org/wiki/Timber (http://en.wikipedia.org/wiki/Timber)