UPDATE: Since I posted this, things have changed considerably. I am updating it now to reflect the current layout. (January 9, 2007)
UPDATE 2: Replaced the Club Sega link and checked on Gamengai map to find it dead. Added Trader link to map. Added a Google map denoting these places plus Kaosu Kan since gamengai map is not working.
Club Sega is your single most helpful landmark. You should see it when you hit the main drag coming from the JR station (follow the Electric Town signs). Club Sega is red and it stands on the corner.
The street to the left of Club Sega leads you to a little center of import goodness. Follow it down to the first corner. There will be a Trader on your left. They carry import titles of every system, but as it is a used games shop, the stock always varies.
Across the street from Trader, you will find two import shops, Messe Sanoh/Game Chaos and Game Hollywood.
Street level, purple sign with orange letters, and a playable 360 kiosk (usually)
It's on the 5th floor of a small building across from the Trader. Look up and you should be able to find the sign, then hop in the tiny elevator.
The shop is on the main drag (Chuo-Dori) just a little north of Messe Sanoh (the regular one, not the import shop I mentioned before) on the west side (the Club Sega side). They have a yellow sign with blue standard-looking font that says "Trader 2", and the shop is small so pay attention. When you come to a corner with an Excalibur/Fauxbucks, it is just up ahead. They carry import used titles just like the other Trader, and sometimes they have a better selection (probably because they get less traffic).
Here's a map from Trader's site. It shows all their Akihabara locations.
An Interactive Map from Gamengai (Update: Seems to be dead, but I'll leave the link here just in case something is corrected in the future.)
Since Gamengai is not working, I made a map myself using Google Maps. I don't think this existed in 2006.
Edited by thakingrocka, 29 September 2009 - 01:39 PM.
New Info, Google Maps