Parts Express comes to mind, and DigiKey, Mouser, Jameco, etc.
I used to get Allied and Lafayette catalogs when I was a kid.
Sure do miss Radio Shack - it was a super difficult thing to watch them adapt to the times. It was really an impossible effort.
Yes, at work we order all the time from DigiKey, Mouser and Newark Electronics.
Oh man, Lafayette Electronics brings me back to the 70s! They had a big store on Bedford Ave in Brooklyn and I was there all the time, getting cables, connectors, testing vacuum tubes (remember that!), buying all sorts of nerd equipment. They were big at the time, sold their own brand of hifi gear (Criterion?) but also other big name stuff too. A blast from the past for sure, I wish I had kept some of their catalogs just to leaf thru and remember.
They had one guy worked behind the counter, he was the most near sighted person I have ever met. Super thick glasses, he would have to hold the catalog almost to his nose to find the part number. But he was that kind of person who knew about almost everything in the store, Canon connectors and Jones plugs, 6L6 tubes, Belden wire. You just assumed he was a ham radio guy. And he was good with that new fangled solid state stuff too!