Alright, done deal:

IBIS AMSTERDAM CENTRE HOTEL
Stationsplein 49, 1012 AB Amsterdam
Tel: +31 20 638 30 80 Fax: +31 20 620 01 56

We have booked 40 twin rooms to host 80 sponsored participants
8 - 11 October 2009
American buffet breakfast included

I think this defines the default location. The twin room is 146€/night with breakfast. Not too bad considering that it's in the very center of the city and well connected to the Summit venue:

Walking: 2.6 km – about 32 mins
By taxi/car: 6-10 mins
There is a S103 bus that actually connects venue and hotel quite well

Now you decide who goes to which room, plus any other info / requests / exceptions. We at Nokia are basically done with this task.