The Castleberry Hill Art Stroll is the second Friday of most months, from 7 PM to 10 PM. There is a hand-out map that evening available in front of Bottle Rocket (180 Walker St. SW). Also, check Elliott Street Pub - they usually have an event like an iron pour going on.
There are usually pop-up galleries for the Art Stroll, but these cornerstone galleries are typically open for the art stroll:
Joining or attending the Castleberry Hill neighborhood association meetings is a great way to get involved in the neighborhood, meet neighbors and learn about neighborhood issues. The meetings are the 3rd Monday of the month at 7 PM. The location of the meeting varies, so check the website for details. Also, meetings may get moved when they fall on a holiday.