Mouser is a good source. The downside is that a couple of times a year, you will get a catalog bigger than a library dictionary showing up in your mailbox.
OK, not a downside to people working on modern stuff! I repaired, restored, rebuilt, and cloned old guitar tube amps, and I needed to be able to stock up on resistors, capacitors, etc, and Mouser was the best source for that.
Radio Slack has lost that ability, and was always more expensive anyway. If I HAD to hit RS for parts, I always felt bad about giving them my money, because I knew how affordable those components were on the open market. I don't mind paying 2-10x the going rate for a component when I need it, but RS was selling stuff (per item) that I could get from Mouser per 100 at the same price.