Websites for finding accommodation in Budapest:

http://www.ohb.hu/
http://deals.hotels.com/
www.save-on-budapesthotels.com
www.HotelClub.com/Budapest_Specials
www.gtahotels.com
http://www.booking.com/

Accomodation in Hotel SAS Radisson Beke (Conference Venue):
http://www.ohb.hu/beke/index.en.html
Single room: 152 EUR/night
Double room: 169 EUR/night

Other Hotels in the Vicinity:
(for updated prices, please check respective websites)

5 stars:
Corinthia Grand Hotel Royal
http://www.corinthiahotels.com/hotel.asp?h=5

New York Palace Boscolo Hotel
http://volll.at.11am.hu/boscolo/

Corinthia Aquincum Hotel
http://www.corinthiahotels.com/hotel.asp?h=4

4 stars:
Danubius Hotel Gellert ****
http://www.danubiushotels.com/en/budapest-hotels/danubius-hotel-gellert-budapest

Danubius Hotel Astoria ****
http://www.danubiushotels.com/en/budapest-hotels/danubius-hotel-astoria-budapest

Cotton House ****
http://www.booking.com/hotel/hu/cottonhouse.html

NH Budapest Hotel ****
http://www.booking.com/hotel/hu/nhbudapest.html

3 stars:
Juditapartmenthotel ***
http://www.booking.com/hotel/hu/juditapartment.html

Central Dominik Pension ***
http://www.booking.com/hotel/hu/central-dominik-pension.html

Hotel Papillon ***
http://www.booking.com/hotel/hu/papillon.html