>>1002848universalcycles - easiest site to use. slightly higher prices, wait for discount email and buy
somafabrications/IRD - I can't hate on these guys because they have sweet bar tape and handlebars
nashbar - if you priority is dirt cheap, this is the site for you. Occasional amazing deals
jensen - my all-time favorite. Low on selection but shipping to the east coast is faster than universal cycles, and prices are a little better
ebay - the ultimate way to buy shit you don't need and still be really happy with it. Lots of good deals to make up for the stuff you shouldn't have bought. Consistently the best prices on major brands if you are patient
aliexpress - Incredibly cheap shit. $2 for a headlamp. $0.50 for a compass. $1 for a bottle cage. 50% chance it will smell like burnt rubber and human suffering. But there ARE some good deals on there, watch out for bootlegs and basically everything. Do not buy carbon from here