Lets see, on the NE side - the main drag (Highland) through Morningside down into and encompassing Virgina-Highland. IMO, one of our best areas.
Emory Village for a couple of blocks. The Buckhead Village area. Little Five Points, Inman Park & Lake Claire. Downtown Decatur, Cabbagetown, Oakhurst, East Atlanta Village, Grant Park and West End. Sections of Midtown, particularly around the edges of Piedmont Park.
Some burbs have done a nice job with their downtowns. Roswell, Marietta, Norcross (on the cusp of a BOOM), College Park (on the cusp of a mini-boom), Duluth (still evolving) and Buford (ditto). Watch out for Lawrenceville, and especially Woodstock - it's next.
Anybody think of any I've left out?