It's true that our Web Hosting plans are generally the perfect solution for new and growing websites. Once you outgrow your Web Hosting account, our support team can seamlessly move you into one of our Managed VPS Web Hosting accounts. Concerned that your site will continue to grow from there? Don't be! Once you outgrow your Managed VPS, we'll move you right into one of our Managed Dedicated Servers.
koding.com has a free VM running Ubuntu. The specs are pretty good, 1 gig memory for example. They have a terminal online you can access through their website, or use SSH. The VM will go to sleep approximately 20 minutes after you log out. The reason is to discourage users from running live production code on the VM. The VM resides behind a proxy. Running web servers that only speak HTTP (port 80) should work just fine, but I think you'll get into a lot of trouble whenever you want to work directly with other ports. Many mind-like alternatives offer similar setups. Good luck!
Lightweight, fast and reliable - these are the core tenets of CentOS. It is one of the best Enterprise-level operating systems that aims for speed and stability, without cutting out security. Inspired by Red Hat Enterprise Linux, CentOS is also a formidable option for VPS hosting. When in doubt, pick the go-to web server operating system around the world. Power, robustness, and flexibility guaranteed!
The force driving server virtualization is similar to that which led to the development of time-sharing and multiprogramming in the past. Although the resources are still shared, as under the time-sharing model, virtualization provides a higher level of security, dependent on the type of virtualization used, as the individual virtual servers are mostly isolated from each other and may run their own full-fledged operating system which can be independently rebooted as a virtual instance.