While catching up in the Engadget Podcasts they referenced businesses 'cross-linking' and it's benefits.
The idea is that it is beneficial to a business to 'cross-link', i.e. refer to another business, when it may help the customer. For example, a potential customer walks into a clothing store looking for a certain outfit. The sales rep, realizing that clothing store doesn't stock the size or style the customer needs, says "Sir, I'm sorry we don't have what you want, but I believe I've seen what your looking for down the street at the other clothing store in town." This may seem counter-intuitive, but I believe it a good practice.
What this does is 1) suprise the customer in a pleasant way. This is a sales rep that is not concerned with making money, but making a better experience and happier choice for the customer. They customer may not conscientiously realize this, but they feel it; and 2) the customer will likely return to the first store when looking for items because they appreciated the good assistance and more importantly, the sales reps may point out when a better deal/desired item is available elsewhere. Therefore, the person can be reasonably confidence in 'one-stop shopping'.
I worked for several years at Babbages computer stores in the King of Prussia Mall, PA. We were one of the few software shops at the time that did not work on commission. In fact, we were encouraged to recommend the customer to other competing software stores in the mall if that store had what the customer wanted and we didn't or even, sometimes, when it was cheaper at the other store.
There were many instances of seeing returning customers I had pointed to one of the other stores returning on later visits because they appreciated my honesty (no ma'am, that game is really not fun, game B is better, but we're sold out, they're selling it downstairs at Store D) and wanted to return that good nature and also felt good that they would get the best deal by first stopping at our store.
Of course, I don't work in retail anymore (though I do miss it at times), but the idea is a good one to apply to other companies, great and small.