One spot that comes to mind is the plaza outside the Akihabara Electric Town North exit. There is a long pedestrian bridge leading from the plaza to the UDX building. Many cosplayers, street singers and vippers congregate here almost on daily basis.

A quick search on google image turned up this pic. This shot is taken from the train station exit. You can see the plaza is on the right, the pedestrian walkway is in the middle and the UDX building is straight ahead. You can barely make out the white on black UDX sign through the walkway covering.

On Sundays, the police close the Chuo-dori, the main drag through Akiba, to vehicle traffic. People have cosplay photo shoots and concerts on the street (although the Manseibashi police insists that no one stops.) IMO this is the best time to go to Akiba.

The hiking season for Mt. Fuji July and August. It is cold in the other months, and not recommended to scale or hike Fujisan.

There is always kaitenzushi...