The NoFrills grocery store in Canada offers price matching. You simply show them a flyer and they promise to match the price as they sell it to you. I see that Wal Mart has also adapted to this new trend and I do this a lot with their electronics and DVDs. The resource is there, but how many of you actually bother to do it? I definitely do it and I can't believe how much you can save if you do it. It's something like couponing.
I usually forget about doing this to be honest. I can just imagine how much money you can end up saving by doing it. Maybe if one of these days I find myself in No Frills, I will show them a flyer from another rival supermarket like Food Basics, which is currently offering a huge $0.99 Mania sale.
I love to do price comparison, It helps me save money when comparing prices. I like to take prices of paper clips to stores where I shop and show them the price to receive the item for about the same or cheaper value.
We have several supermarkets promising to price match where I live. I never actually had one of them match a price from somewhere else (mainly because buy most of my stuff online), but as far as I know they are pretty good about this. And they have to be, as they publicly announce that as a guarantee, it would be a false advertisement if they didn't fulfill the promise and it could generate legal problems for them.