These are important tools when dealing with memory upgrades, but there are more resources on the site which are also worthy of looking at. There is a Mac memory section, and of course you can purchase by individual memory type, such as the now harder-to-find SDRAM of yesteryear, as well as high-performance Ballistix DD2 and DD3, Flash memory cards of all types, and Solid State drives.
How is the service? Well, I ordered memory from Crucial.com last week, and it took a mere 2 days for it to arrive! Excellent service by anyone's standards. So, this site is honestly all you'd ever need to use for upgrading your system's memory. That's why they call them "The Memory Experts." And guess what? They didn't pay me to say any of this.