I have transcribed the great Sheldon Brown's seat post size database into a Google docs spreadsheet with a column at the end for listing original parts, frame details, and other relevant information such as if the bike is a hybrid. There are separate sheets for road, mtn., and BMX bikes. If you can contribute anything it would be appreciated by everyone. Together we can surely create something great with the variety of bikes and number of enthusiasts on BFs. You can insert a row if you know how, or just add your bike at the end in the first empty row and I will sort the sheets occasionally. It can be found here seat post spreadsheet