In one of my first posts, I advised against Vancouver if outlet shopping's a high priority. I say this, not because I'm an outlet shopper, but because it's a surprisingly common question. I've read numerous forum postings where international tourists are hoping to take advantage of the outlet shopping when they come to Vancouver, but of course, there isn't any. I feel people should know this ahead of time.
Unlike the USA - a country known for its massive discount factory outlet malls - we don't have anything like that anywhere near Vancouver, and to be honest, it's not really a Canadian phenomenon.* We do have big box stores out in the suburbs (especially in places like along Richmond's Bridgeport Road or along Hwy 10 in Langley's Willowbrook), but they're not factory outlets, they're just regular-priced shops in oversized spaces.
Saying that, while we don't have factory outlet malls, there are some individual outlet stores scattered around, but they tend to be local brands and generally not international designers. There are a few exceptions, like Roots, which has an outlet store on Grandview and Boundary. A Google search for "Vancouver outlet stores" will give you a better picture of what else is out there, but you'll ultimately discover that outlet shopping is just not Vancouver's strength. Not only that, but they're not generally in convenient locations. Unless you were specifically seeking that one particular store, I wouldn't waste your time.
If you did want to go bargain hunting for designer clothing, again, Vancouver fails at that too. The only store that I can think of in Vancouver that comes close is Winners. Winners at first feels like a second hand store, until you realize that the merchandise is designer and new. The fact that it's often a fraction of its original price is also a nice bonus! But you do really have to pick through the clothing, hence my comparison to a thrift shop.
Otherwise, the closest outlet shopping malls are located in the USA along I-5 in Washington state. The best one that's close to Vancouver is arguably Seattle Premium Outlets in Tulalip. If you don't mind border line-ups and a two hour drive one way, that place can definitely satisfy an outlet shopper.
* Edit (Jan 8, 2009): After recently spending time in Québec, I noticed a sprawling outlet mall just west of Montréal. I should have known better than to generalize about Canada as often what one observes in one's region doesn't necessarily mirror what's happening in other regions. In this case, while outlet shopping isn't a Vancouver phenomenon, it certainly exists elsewhere in Canada.