Robin Kelsey has some great photos of new graffitti on the "Tech Wall" -- the park at the old Technical High School near Bronson & Slater.
(Also: make sure you check out another pic by Robin called "Oh no!" We've been meaning to recommend this fun pic for a while!)
For more pics of graffiti in Ottawa, try a search on Flickr for "Ottawa Graffiti". There are some great recent galleries uploaded by MK_Escobar and ravensview. Ravensview also has a great web site all about graffiti.
Related: Ottawa Photography Guide