Boating (sailing, rafting), Ottawa
Rafting on the Ottawa River is highly recommended; it's considered one of the best whitewater destinations in Canada. The best known companies are Wilderness tours (http://www.wildernesstours.com/) and Owl Rafting (http://www.owl-mkc.ca/owl/). The departure points are somewhere around 1 to 1 1/2 hours drive out of the city, but well worth it from what I hear. It's cheaper during the week & in early / late summer, and also less likely to be crowded. Kayaking is also available, and I believe there are even some 'gentler' rafting trips for families. This is a great way to escape the nasty heat and humidity of Ottawa in the summer!
Equipment: Even if it's cold, do NOT wear wool! You'll sink. Trust my roommate, who also has a picture of herself being caught by the belt in midair (by a guy named Brutus!!) after being flung out of the raft. :-)
I was lucky enough to have a friend at JDS Uniphase that had a 26 foot sailboat. So, during the warm months, we'd go out sailing in Britannia Bay.. It's not a large bay, but you can sail for several hours.. there are several small islands you can anchor off of, and swim to shore...
Here's a picture of a sailboat we were towing in Ottawa one time..