Fast on the heels of Amazon EC2 comes AppLogic's 3Tera (tip: R/W web):

AppLogic is a grid operating system for scalable web applications and services. It enables transactional and streaming applications to run on grids of commodity servers.

As Read/Write Web points out, you "almost [need] a Comp Sci PhD from Stanford to read 3Tera's press release".

Most webapps are assembled from existing well-known components: Apache, Java, Python, Ruby, Linux, shell scripts and so forth. If AppLogic requires you to code to their library and platform, I doubt there's much of a future in what they're doing; if they allow you to bring existing components into their environment or provide standardized versions of the same, it could be very very cool.

I'm surprised Sun isn't offering a "Java Compute Cloud" to run Java apps and webservers.