The Discovery Centre in Halifax (Nova Scotia) has an online version, at:

http://www.cfn.cs.dal.ca/Science/DiscCentre/DC_Home.html

Three of the most interesting - and different! - discovery rooms I've seen
lately are at the:

Australian Museum (Sydney)
Auckland Museum
Australian War Memorial (Canberra)

Unfortunately, I don't think any of these has an on-line version. We expect to
open a discovery room in December and will add an on-line version of it as soon
as possible.

Harry Needham
Canadian War Museum