Obviously the lack of any serious mountains nearby limits the options for snowboarding near ottawa, but there's plenty of snow for a long part of the winter season, and there are hills to the north across the border in quebec.
Mont St-Marie is the bigget and best, with two hills and about 5 or 6 runs on each, lasting less than 5 mins if you flatline it! (in the summer there's a golf course here, so don't expect the rockies!!)
Still there's a board park, and some fun to be had on a spare weekend/afternoon. The charges are reasonable - at least if your snow starved from london!
Its also worth checking out for biking/hiking in the summer.
Equipment: Rental is available, you can get a good all-in price and worth considering as the coverage can be patchy at times.