Canon produces a quarterly Magazine that is distributed to it's Canon Pro Services (CPS) members, titled; CPN Canon Professional Network.
If you are a Canon User with a minimum of 2 x Pro Bodies(40D or above) and 3 x L Lenses, you can join CPS Silver service by registering and listing these on the Canon CPS online portal
The Magazine is a mixture of articles from Pro Shooters providing anecdotal references and experiences as well as sections on tips, tech solutions, commercials and brand marketing techniques etc.
I believe Nikon also produces a Tri-yearly magazine called Nikon Pro.
Please do take into account, I live and work in UK and Europe and therefore, cannot guarantee that the CPN magazine is available outside of this region. There may also be an annual cost for different countries and different tiers. There is no current charge for it in the UK.