Apparently Oracle has an "early access" version of Java SE for ARM. I'm pretty sure that there are a few open source VMs floating around with ARM support, but I wouldn't count on any of them being full drop-in replacements for Oracle Java.
(Obviously there's a bunch of J2ME and other embedded implementations, but I assume that's not what you're looking for.)
Nope. We're going to build a small compute cluster for java 7 code. It's for a few dozen cores so nothing huge. I love these embarrassingly parallelizable problems so the idea of using cheap servers has some appeal to me. Though the individual job run time matters too so we need something somewhere in the middle.
(Obviously there's a bunch of J2ME and other embedded implementations, but I assume that's not what you're looking for.)