Online shopping for music

For classical: ArkivMusic. They have an unsurpassed selection. It's also an easy site for looking up recordings by performer, composer, conductor, or label. Not the lowest prices, but when you can't find it anywhere else, chances are they'll have it. Great customer service. Get on the email list to be informed of sales—it's the time to buy for competitive prices.

you can also try BetterRecords and AcousticSounds, more mainstream on the order of MusicDirect although Betterrecords is a good spot for one off's.
Heard good things about CD Baby, lots of inde artists too

Shopping online is very convenient. You don't waste time on the road. You can buy any item while at home. Including toddler boy pants. After all, not always a small child likes to go shopping. With the help of the Internet, you can order any quality item.

Bull Moose Music has both new and used.

Pop Market

Plaid Room Records

Discogs

There are literally dozens of places you can buy music online.  Many cater to a specific type of listener, so knowing your listening preferences would help.