Well, maybe not the ultimate, but these are the places I go, and recommend you go to as well. All of them normally have something worth checking out in the musical department. I can't believe this is the first time I thought about typing it all out...
*10 High: 10 High is located in the Virginia Highlands district and is nestled directly beneath the Dark Horse Tavern, right at the corner of N. Highland and Greenwood Ave. There's a couple of pay lots located across the street and right past the venue, but if you don't mind trekking a couple of blocks, you can park on the street anywhere surrounding the place (just don't block driveways or fire hydrants, because your ass will get towed). Those streets are St. Charles, Drewry, and Briarcliff. 816 N. Highland Ave., Atlanta, GA 30306 (Google Map)
*Blind Willie's: Also located in the Virginia Highlands a couple of doors down from 10 High, this blues venue is always packing. The parking situation is the same. Blind Willie's is found next to Limerick Junction and Osteria. 828 N. Highland Ave, Atlanta, GA 30306 (Google Map)
*The Drunken Unicorn: Fueling the fire for indie-rock bands from all over the country, the DU is in a prime location. If you don't know it's there, you'll never find it, though. Right off of Ponce, over by landmarks like the Local, Clermont Lounge, and Liberty Tattoo, the Drunken Unicorn is right behind the fairly new Chipotle and across the street from Kroger and Green's Liquor Store. There is a parking lot with an ATM where you can park for free, or you can do as I usually do and park in the Kroger parking lot and walk across the street. 736 Ponce de Leon Place, Atlanta, GA (Google Map)
*The EARL: Another venue that caters to national indie acts, the EARL is in the East Atlanta village, and the actual venue is behind a door past the bar. You can park anywhere behind the buildings around the EARL, sometimes free, sometimes for a fee depending on the day. The East Atlanta Village is located right off I-20, and the entrance is stuffed in between a Shell and Citgo gas station. 488 Flat Shoals Road, Atlanta, GA 30316 (Google Map)
*The Five Spot: Small and intimate venue next to the Variety Playhouse on Euclid. This place caters to local acts and artists. Tip Dusty the bartender real well because he's the poop. You can park in the lot in between the Five Spot and Variety. 1123 Euclid Avenue Northeast, Atlanta, GA 30307 (Google Map)
*The Loft/Vinyl/Center Stage: All three of these venues are located in the same building over by Atlantic Station in Midtown at the corner of 17th and W. Peachtree. There are parking lots all around the joint, charging anywhere from $5-$15. Vinyl is located to the left of the building, while Center Stage (formerly called Earthlink Live) and The Loft are on the right side. The Loft is, appropriately enough, upstairs. 1374 W. Peachtree Street, Atlanta, GA 30309 (Google Map)
*Smith's Olde Bar: You should know this place because they have the best sound in the city. Located in Midtown, over by Ansley Mall and right next to that Cowtipper's place. You can park either in the parking lot of the strip mall directly behind Smith's, or across the street by the Exxon, and all parking is free. Woohoo! The music is usually located right past the bar and up the stairs. 1578 Piedmont Ave, Atlanta, GA (Google Map)
*Star Bar: Located in the lovely Little 5 Points area, Star Bar is directly across the street from the Vortex, where I eat way too often. When on Moreland, look for the big skull and park your car in any of the pay lots located around it. Star Bar is on the corner, right by abbadabba's. They have cheap beer! 437 Moreland Ave, Atlanta, GA 30307 (Google Map)
That about covers it for now, I think. If there are any others I should add, email me, or leave a comment. Grassy ass.