Yeah the war museum is open so far as I know.
One thing I really like to do when I go to Ottawa is attend Question Period in the House of Commons. It's pretty awesome that you can go and sit a few feet from the Prime Minister and listen in on all the goings on. The best way to get in is to contact your local MP's office (whether you voted for him or not) and ask for a pass. That way if he (or she) is not busy you can also go into the west block and meet with your MP in their office when you pick up the pass.
I'd also suggest a trip over the river to Hull. The musem of Civilization is an oustanding building. Probably one of the most intersting building in Canada. The exhibits in the museum itself a pretty standard, mostly CDN history stuff that you probably are already bored with. One good thing in the museum (and it's in the free area as I recall) is the huge native scuplture that is depticted on the back of our new $20 bill.
Charlatan covered everything else, except for Zaphod Beeblebrox's Night Club at the Edge of the Universe. It's a great live venue in Byward Market, check ther schedule here for acts
http://www.zaphodbeeblebrox.com/