Ok..... Since everyone is saying I should chime in, here it goes.
Places to buy music: (all in the French Quarter)
The Louisiana Music Factory (tons of local stuff)
Magic Bus Records (lots of rare stuff)
Tower Records (great jazz and local section)
Virgin Records (it's freakin HUGE)
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The Mushroom (outside the F/Q)
Jim Russell Records (outside the F/Q)
Local Bands worth buying:
Kermit Ruffin's and the BBQ Swingers (4-5 CDs)
Bob French & Friends (buy all 3 CDs, they showcase many local greats)
The Preservation Hall Jazz Band (mostly 2/4 stuff, but it's still sweet, and authentic)
The Jazz Vipers (2 CDs)
Others:
Juanita Brooks, Germaine Bazzle, Sista Teedy, Henry Butler, Davell Crawford, John Boutte, Kimberley Longstreth, George French, CAC Jazz Orchestra.
That should get you started. I'd be happy to show you around when you come down.