I personally like The Forum at Peachtree Parkway especially on a nice day. I'm not much of a Mall person, so this works for me. Nice shops, places to eat, coffee... Trader Joes is there too!
I also like the Dekalb Farmer's Market. Very unique. Things from all over the World.
Lil Five Points and surrounding Virginia Highlands is also a great place... lots of little shops, places to eat and hang out, and just really laid back.