Allied Electronics
Not as wide of a selection as Digikey, but prices tend to be a bit better on ICs. I have ordered from them a few times. Shipping is reasonable, and everything is very safe and overpacked. Often better low volume prices for than Digikey.
The Electronic Goldmine
Sorta like AllElectronics, but with even weirder stuff. AllElectronics and The Electronic Goldmine tend to stock some of the same components, but they tend to be a bit cheaper on Goldmine.
Jameco
I ordered from Jameco once, I don't like their site interface as much as Digikey, but prices are ok.
This is from the perspective from a hobbyist, not an trained engineer