Start with harlanjberk.com There's lots to look at there, in every price range, and most everything is photographed.
With that all I can say is AHHHHHHHH. That place is here in Chicago, downtown on Clark Street. I USED to go there a lot. Actually for so long now that it was a different name way, way back then. At first when they became Harlan J. Berk they were pretty good on coin types, grades and prices. Then for the last few years they changed to overpriced, poor grading, lots of cleaned coins, rude and ignorant people in the store. Being around there so much it used to be I would go there as much as a place for food until they got stupid. Lots of stories about junk coins, cleaned coins, overpriced, etc.
Now I cross the street so I don't have to be on the same side as them.
As to on line dealers the only ones I've tried is Miller's Mint, VT Coins and JMS coins. Miller's Mint is great, VT Coins is or was OK but never tried them in the last few years. JMSCoins is well into the very expensive stuff. With a multitude of coin shows, coin stores, flea markets, on line coin dealers are last on my list.