Local Farmers Markets have been springing up over the last few years in Vancouver and I for one couldn't be happier. While each one has it's unique feel and character, I prefer to shop close to home at Trout Lake Farmers Market.
On any given Saturday between May and October you'll find growers like Helmer's Organic Farm and Hannah Brook Farm (we use both) selling their unique produce as well as numerous other artisans.
There's also the winter market to check out at Wyse Hall. The market is held every second Saturday from Novermber to April. Now it is possible to shop local year round!
The eat local website is a great source for information on the various markets in the Vancouver area. There is also a complete list of vendors and special event listings.
For other markets throughout the Lower Mainland, I'd suggest heading over to the Welcome to BC site.