Nutritional Yeast

Where can I find this?  A really good cream of broccoli recipe calls for it and Trader Joe's doesn't sell it, nor does Jewel--my local grocery store.

...and what is the difference between the powder and flakes?

It's almost always in the bulk section at health food stores--I'd check there first, but otherwise, Wild Oats and Whole Foods have it.

The powder is a powder, and the flakes are flakes....  there is no difference other than the texture.