I second the love for MakeYourOwn.Buzz. The same folks also own Chemistry Connection and SaveOnCitric. Depending on where you live, it can pay to search all three sites to see which one will get you the best deal.If you want a cost effective source for surfactants for making syndet bars, I recommend makeyourown.buzz. This is the version of SCI I recommend, too: Sodium Cocoyl Isethionate Powder
They also have SLSa and CAPB and both versions of BTMS. They have cetyl alcohol and even silicones if you want to put some in conditioner bars. Everything is waaaaay less expensive than other sources. I mean some of the more expensive ingredients are like half what others charge. And their shipping charges are not outrageous, either. They have excellent quality products and responsive customer service people.
They didn't pay me to say this. I'm just a really happy customer. They messed up my order one time but they made it right really quickly.
I probably would never have started making shampoo bars if I had to pay what everyone else charges for the ingredients!