Advance Electronics has been very good. I've been bringing my Macs there for years, and they've been fairly prompt. However, I've heard good things about the University of Manitoba Bookstore, but I haven't tried it. www.advance-pro.com
MacHelper. They only sell and service Apple products. And threads like this are great for newbies like myself, I work in the graphic arts trade and I have been telling lots of Mac users at work about ehMac since I discovered it a while ago.