Personal cloud computing - running multiple virtualized machines (Xen, OpenVZ, VMWare, etc) on your desktop or a single personal server - may be an emerging pattern. Vidar Hokstad writes about his setup, in which he partitions scratchpad machines (for play and experimentation) from long-term machines (for backups and archives).
On the Heroku team, we develop on what we call “dev clouds” - a set of EC2 instances spun up just for the day, for each developer. Each dev cloud is a miniature version of our production cloud. This works extremely well, but now that we have a decent-sized team, it’s a bit pricey to run so many instances all day long. It also requires pretty good connectivity to get any work done (not always possible when traveling). And it pretty much rules out use of local tools, like TextMate.
Personal cloud computing could be a replacement for this approach. Run a set of local virtual instances, which mirrors the machine layout and operating system installs found in the EC2 cloud. A dev cloud on your desktop.