Even though I don't have a direct answer, my advice is to start with the typical Top 10 programs, which tend to be strong across the board. Identify the faculty that specialize in Distributed Computing, and then branch out from there by looking at coauthors or referenced authors in their listed papers. After a while you should start to see a trend developing of professors who are consistently referenced by others. CiteSeerX and Google Scholar are really helpful at finding how often a paper is cited by others.
And I say all this because your potential advisor's reputation is far more important than a departmental or specialization ranking. When you go to apply for your first academic appointment, it will be your advisor who gets you the job. But you didn't specify MS or PhD, and I imagine this is far less important in industry.