Money Tip: If you have time to do more than 1 museum trip, then look for combo deals. Also, you are likely to get a better price online (if you can find a groupon, even better!) than landing there to buy them.
World War Museum in Ottawa
One of the favoured museum trips in Ottawa is the spectacular War Museum - http://www.warmuseum.ca/
It is based quite close to the Parliament Hill and is a thoroughly enjoyable half day if you are into History of the World wars -
Complete Details - https://en.wikipedia.org/wiki/Canadian_War_Museum
There is some great trivia around this place, and here are some of them -
1. The unique design is actually setup to point the upward curve towards the Peace tower of Parliament hill (it is lined up exactly to face the flag on Parliament Hill)
2. If you pay close attention to the "fin" in the image above, it has morse code for "Lest we forget" - in honor of all those brave souls who laid down their lives for this great nation!
3. If you are a fan of the Commando comics (https://www.commandocomics.com/), then this is a place that has to be on your visit list -
4. The museum isn't pro-allies, all kinds of memorabilia are around.
Summary
On a personal note, we could spend an entire day here (our last visit was about 3 hours as part of the Hop-on/Hop-off tour - and we felt we were short of time). So we are planning to visit again this summer.
Here are some additional pics to pique your interest -
A Panzer IIC Tank
A 60cm Searchlight
Pic says it all
Other Museums in Ottawa
Travel: Canadian Museum of History in Gatineau-Ottawa
Travel: Diefenbunker Museum in Ottawa
Travel: Canadian Aviation Space Museum in Ottawa