Enter your serial number (open System Profiler so you can just copy the number from the Hardware tab) and you'll see your model name on the left.
You can also download Mactracker. You can find both your model number and serial number using with it. It's also handy for tracking when warranties expire and what computers and peripherals you have.
Comments
Easiest way to find the model name is to use the warranty assistant: https://selfsolve.apple.com/GetWarranty.do
Enter your serial number (open System Profiler so you can just copy the number from the Hardware tab) and you'll see your model name on the left.
You can also download Mactracker. You can find both your model number and serial number using with it. It's also handy for tracking when warranties expire and what computers and peripherals you have.