There is no need 'at the moment' for a seperate place.
The project & competitions forum is a good place so long as the 'series' is a genuine project where lots of people are involved.
The Tracks forum is also a possibility, but that would be more of a 'thread about XXXXXX style of track'
There is a subtle difference between the two kinds of idea.
I perfer to end up with a 'Tracks In Series' forum by one day realising we have too many stickies which could be moved to that place ^^