cheapies: sennheiser 238 - http://www.sennheiser.com/sennheiser/home_en.nsf/root/privat...

at the desk: sennheiser 280 (i really wish they didn't have a coiled cable) - http://www.sennheiser.com/sennheiser/home_en.nsf/root/privat...

on the bike/plane/train: etymotic er-6i - http://www.etymotic.com/ephp/er6i.aspx

i recommend headroom for buying/research (http://headphone.com/). they review most of their products and will tell you which ones are junk (even ones they sell) and which aren't worth the high price tag.