<p>So far I've read some blog articles about cloud computing and services for hosting applications in the grid. </p>

<p>If I'd wanted to have a web application running in the cloud for as little cost as possible, what would be the best solution?</p>

<p>Let's assume the following configuration:</p>

<ul>
<li>J2EE web application </li>
<li>Any free database (MySQL, PostgreSQL)</li>
<li>Any web container to deploy the web application to</li>
</ul>

<p>What application stack would you suggest to be the best combination of services to </p>

<ol>
<li>host </li>
<li>deploy</li>
<li>run</li>
</ol>

<p>web applications? </p>

<p>As an additional requirement, the services chosen shouldn't require a lot about server management like firewall settings etc.</p>

I have investigated
Amazon's ec2
solution recently. It is quite good and there are many pre-built boxes that you can use if you find one that suits your need. I think there will still be some server management involved...you cannot get away from that. But the pre built boxes will make it easier.
The cost is reasonable as you only pay for what you use.
[EDIT] The pre-built boxes are called Amazon Machine Images (AMIs).