Or http://www.bamboosero.com/ if you are not so wealthy. Plus you support some small minority businesses: a double whammy!!
I do wonder exactly how environmentally bamboobikes are. I presume they are, but am not certain about the glues etc. Also, with these bikes it’s interesting to wonder how they are transported. If it is boat transport from afar that’s not really a problem as boat transport does not use a lot of energy. Planes is a different matter of course, so if you order a bike from the U.S.A. that may be tricky.
Regarding more conventional bikes, steel is better than aluminium as it requires less energy to make. I do not know how energyconsuming titanium and carbon are, but I presume they need quite a bit.
Of course one of the most environmentally friendly ways is the second hand market. There must be several companies that do up old bikes and make them anew. Recycling in optima forma!