There is a great deal of information available about Canadian veterans online.
For the years before 1914
Canadian Military Heritage Project
For the First World War
Canadian Expeditionary Force Study Group. This is for the real die hards amongst you it is very technical.
http://www.cefresearch.com/phpBB2/ or http://cefresearch.com/matrix/index.html
Canadian War Museum(also information on W.W.2) http://www.warmuseum.ca/cwm/home/home
Canadian Great War Project http://www.canadiangreatwarproject.com/
Canadian War Brides of the First World Ward blog http://ww1warbrides.blogspot.com/
Library and Archives Canada. For online records of soldiers and other information useful in your research
For the Second World War
Canadian Virtual War Memorial
Commonwealth War Graves Commission http://www.cwgc.org/
Library and Archives Canada above.
Legion Magazine: Last Post: Dealth Notices. Most info here relates to servicement who passed away after January, 1989.
For a transcript of a veteran who served in the Second world War you can send away to Archives Canada for copies of their service records. Should you need help getting them let me know and I will guide you through the process.
This is a short list. There is a great deal of information out there.
Also keep in mind that for both World Wars you might also have to access British records as it was not unusual for servicemen to be loaned out to the different services. My uncle, for example was with the R.C.A.F.; however, he flew his Hurricanes with the 65th squadron which was a British outfit, and my father’s Lancaster had a R.A.F. serviceman as co-pilot on his last mission over Germany.