AA LGA-ATL $103 +tax
Found via travlocity dream maps, comes about $133 all in. Should be less on aa.com The fare requires a 1 day stay, and is through 9/30 but has very limited availability - I did find availability for out 9/11 (oy! It suddenly dawned on me why there was availability on that day and not on any of the surrounding ones) and back 9/13.
All flights on this fare connect through either ORD, STL or BNA so there are more miles to be had. Hope this helps someone.