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!
Although multiple VPS accounts are hosted on one physical server, we can run several different virtualized operating systems on that one server. Each of these operating systems will perform as if it was on its own dedicated server, giving you all of the benefits at a fraction of the cost. InMotion Hosting uses Parallels Virtuozzo Container to virtualize the operating system.
I was on a mission to look for new VPS hosting for our new website. It was between Bluehost, Dreamhost, and InMotion Hosting. After a chat with Adam, it is clear that InMotion Hosting is the best choice for us because of the outstanding support. I want to let you and your department know that Adam is doing an outstanding job for your company. I will refer my friends to you guys."

VPS can be a perfect solution for businesses that want many of the features of a dedicated server but don't have the resources to physically host, support and maintain the server hardware. A shared environment won't offer you the same bandwidth or Web hosting space that a VPS will be able to support and there are also many more constraints on the software you can run in a shared hosting environment. In contrast, a VPS will give you the freedom to install, delete, reboot and do all the functions as if you have your own server. You also get an increased level of security as each VPS is isolated and completely separate from other Virtual Private Servers on the same physical server. The environment is secure and protected and each VPS can be rebooted or stopped independently – even if a hacker infiltrates one VPS there is no access to the others using the same physical server.
Users of Shared hosting all share the resources on the server their websites are on. There is no guarantee of RAM or CPU with Shared hosting. Shared hosting also does not provide full root access to the server, as opposed to VPS package where users are given full root access to perform commands and make configuration changes to their hosting environment.
A VPS is an excellent choice for web developers, webmasters, resellers, and for those who run resource-intensive websites. Each VPS Plan under Namecheap operates and performs exactly how an independent physical machine would, featuring security and flexibility for your websites, independence from neighbors, full control over your hosting environment, and Dedicated Server power. The best part? It's all at an affordable price.
In a dedicated hosting plan, a client leases or rents a physical server from a hosting provider. With Dedicated hosting plans, the client has complete control of the physical server and access to all its resources. This is a good fit for companies that have websites that expect a high amount of traffic, that are running intensive CPU applications, and that are hosting enterprise CMS sites.

A virtual server and a dedicated server differ by the number of users that possess resources on a physical server. With a virtual private server, some of the resources are isolated for individual users, but there are multiple users on the same physical server. With a dedicated server, a single user has access to all of the resources of a physical server.
Partitioning a single server to appear as multiple servers has been increasingly common on microcomputers since the launch of VMware ESX Server in 2001. The physical server typically runs a hypervisor which is tasked with creating, releasing, and managing the resources of "guest" operating systems, or virtual machines. These guest operating systems are allocated a share of resources of the physical server, typically in a manner in which the guest is not aware of any other physical resources save for those allocated to it by the hypervisor. As a VPS runs its own copy of its operating system, customers have superuser-level access to that operating system instance, and can install almost any software that runs on the OS; however, due to the number of virtualization clients typically running on a single machine, a VPS generally has limited processor time, RAM, and disk space.[2]
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