With many people rightly nervous about compute cloud lock-in, we seem to be entering an interesting time in the development of compute cloud abstraction libraries and APIs for trying to work around this. I noticed that last month RedHat's deltacloud has become the apache deltacloud (Ruby) incubator project alongside the already existing apache libcloud (Python) incubator project, which has a pretty impressive list of supported providers. An interesting alternative to these is jclouds (Java) with its own impressive list of supported providers. However, just this month, libcloud has announced that they too are working on a Java version of their API.
According to Ohloh, all of the libcloud, deltacloud, and jclouds projects are showing a lot of recent development activity - very good news for those of us rooting for the possibility of lockin-free compute clouds.