Amazon regularly adds new types of EC2 instances to keep up with demand and reflect the capabilities of the underlying hardware.  This week they announced medium & large instances in the M3 class.  Like the other M3 instances, these VMs are backed by Sandy Bridge or Ivy Bridge processors and SSD instance storage; more details on Amazon’s instance types page.

Last year we created a tool to make comparing the price of EC2 instances easier.  With the advent of these new instance types, we’ve updated WhichInstance.com to reflect the new options, improving the interface a bit in the process.  Give WhicInstance a look to more easily understand the costs of running an instance over time, and remember that Amazon reserved instances can save you a lot of money!