Product: Amazon AWS is the big dog in the IaaS space. The company introduced the concept of availability zones and regions and still offers some unique features, like Route 53 (DNS service), ElastiCache (caching service), CloudSearch (full-text search service), Simple Notification Service and Mechanical Turk (human worker service).

Company: Amazon AWS

Key Features:
Download Amazon's Feature matrix

Price Range:
Free basic options available. Standard on-demand pricing ranges from $0.065 per hour for a small instance on Unix/Linux to $0.92 per hour for an extra-large instance on Windows. Full pricing is available here.