My contact in Netherlands suggested me to 'vote' for:
http://www.dezwijger.nl/

It's not far away from the centre of the city and from the rail station. And it should have a very nice atmosphere.

just my 2 cent

You can find a lot of the information also on http://www.iamsterdam.com

Here are some more hotels. It is easy to find a small host because there are many of those. Everything is packed so the middle size is not served well. For big business there is stuff like RAI, but these come with a price.

http://www.artis-horeca.nl (40 till 750 people, east Amsterdam, near the famous Artis zoo)
http://www.kit.nl/smartsite.shtml?ch=FAB&id=6126 (8-600 people)
http://www.marriott.com/hotels/trave...sterdam-hotel/ (700 people, but 5 stars...)
http://www.google.com/search?NH+Barbizon+Palace (500?)
http://www.iamsterdam.com/en/placest...3-cbfd3dd62c99 (1-4000 people; business oriented)
http://www.hotelarena.nl (not sure if they have conferences)
http://www.meervaart.nl (800?)
http://www.iamsterdam.com/en/placest...6-207bc302b135

I've never been in any of these btw!!

Forget hacker conferences. They're usually either small or almost always at campings probably related to the fact that Dutch people like campings very much. And its much cheaper, gives more freedom, and space to roll out the stands, tents, fiber, etc. You need a license/permit for hosting that though. Areas used are for example SNT (University of Twente) and Paasheuvel (near Nunspeet). This is 1+ hour travelling from Schiphol, and these are 'camping' sites. They can host a lot of tents and workshops and so on. These conferences from past: http://whatthehack.org (WTH, 2008) http://www.hip97.nl (HIP, 1997) http://www.google.com/search?q=hacki...ic&btnG=Search (HEU, 1993) http://www.hal2001.org (HAL, 2001) and forthcoming http://www.har2009.org (Hacking At Random, 2009). In septembre, with a bit of luck, its still summer. With some bad luck it'll pour rain all over. You can also maybe integrate the Maemo event with the HAR2009 event!! With your own tent, and some own workshops, and maybe sponsorship...

The halls are mostly focused on commercial fairs but the conference rooms are available in lots of sizes (22 ppl to 1746 ppl and lots of in between sizes)

Good choice. This is actually in a very nice area at the IJ river and very near the Amsterdam central station. There is also a big hotel and lots to do.

see http://www.amsterdamdocklands.com/na...etHeinMap.html for a general impression of the area.

IMO you should ask the folks at De Zwijger what kind of connectivity they have. They're part of Waag Society if I read correct. These folks have multiple gigabit connections. Maybe they can arrange (live) streaming? If so, maybe keep it as surprise. They're rather centered about art, including hardware hacks and such; not so much software libre. Their website is http://www.waag.org maybe its interested if there can be some kind of 'link' made between the 2 projects.