I always use B&H or NewEgg and avoid Amazon, when buying flash memory and SD cards (in order to avoid counterfeits). I also bought an SD card from Best Buy recently because i needed it immediately.

Anyway, as for physical brick-n-mortal presence, I just wished that I had Micro Center where I live, instead of Best Buy, though. MicroCenter has far more inventories, more interesting stuff (like Raspberry Pis in store) and better prices as well.