The city has released "open data" (data that is available for use in mashups and applications, such as maps) following approval by Council today. There will also be a $50k apps contest (details to be announced).
http://ottawa.ca/opendata/
You can request datasets at
http://www.dataott.org/
Also the city provides free access to its internal mapping data through a site called
eMap.
Twitter account @opendataottawa is a good place to get more information.