I started a map of off-leash parks... check it out!
Lower Mainland Dog Parks - Google Maps
As far as beaches, for the ocean, there's also:
Ambleside in W. Vancouver (BIG off-leash area between the tennis courts and the water)
Blackie Spit in S. Surrey (just beyond Crescent Beach)
For fresh water, there's:
Hayward Lake (Maple Ridge)
Jerry Sulina Park (Maple Ridge)
Buntzen Lake (Port Moody)
Derby Reach (along the Fraser in Surrey)
Several others around, I'm sure, those are just the ones I can think of offhand.
BTW, there's a really great forum oriented specifically toward dog parks and dog walks, at
Metro Vancouver Dog Walks - tell'em Groucho sent you