What are the differences between Columbus Tubings?
The Bicycle Info Project has a nice page at http://www.equusbicycle.com/bike/columbus/columbuschart.htm that describes the different Columbus tubesets in layman terms.  The following is a sampling of what is on the site.  The information gets even more specific relating characteristics to particular tubes (e.g. top tube, seat tube, chainstays, etc..)