Cloud services are becoming more and more common now, and I'm not talking about grandma's online backup. Websites and applications are starting to fundamentally rely on services that exist ... out/up there somewhere ... and if you weren't an early adopter, well you had better get into the game, and quick. Here are some resources that will help you get your feet wet:

Amazon EC2 Micro Instance

New customers are entitled one year's subscription to the AWS Free Usage Tier, which includes an EC2 Micro Instance and access to leverage free usage tiers on the Amazon S3, Amazon Elastic Block Store, Amazon Elastic Load Balancing, and AWS data transfer services.

Windows Azure for MSDN Subscribers

Subscribers to the Microsoft Developer Network can activate free, limited access to Windows Azure (Microft's Cloud Computing Platform) which seem to available at three levels of access: Professional, Premium, and Ultimate BizSpark. When you've chosen the plan that's right for you, and you're up and running, make sure to check out the Windows Azure Developer Portal for great resources to get started! If you're not a subscriber to MSDN, you can sign up for a free trial of Windows Azure which allots 750 hours on an Extra Small Compute Instance, 25 hours on a Small Compute Instance, 20GB storage, 20GB transfer in/out, and 100k AppFabric Access Control transactions per month.

Force.com PaaS (Platform as a Service)

Force.com is a cloud platform that combines the four main products of Salesforce.com (Appforce, Siteforce, VMforce, and ISVforce) to create a truly beefy toolkit and a no-holds-barred environment for businesses to create hardware agnostic cloud applications while reducing production and maintenance costs. Join the ranks of Qualcomm, Starbucks, Dell, Kaiser Permanente, Snapple, and the likes and get your Force on (with Freeforce), today!

While there are many free options available to software developers in respect to cloud computing services, they seem to come and go with the tide, so the ones listed here are packages offered by truly adopted platforms that won't be going anywhere, any time soon.