I am the CTO at Palomino, a hardcore DB and Cluster Operations group. We are building big database clusters and operating them using ITIL methodologies, making sure that the clusters we build work well beyond the first few months of usage.
We build HBase, Cassandra, MySQL, PostgreSQL, Couch, and Mongo clusters (among others) using Ansible, Chef, and Puppet either on dedicated hardware or in the cloud. Yes, I know I covered just about every buzzword out there, but it's true. We do all that!
My biggest contributions to Open Source happened in the past: a Dia to DDL tool that has since been deprecated by a great Perl library that does the same, a set of high-volume database tools that have since been deprecated by the Percona Toolkit, and random other things.
However, Palomino is a big-time Open Source contributor, so I'm starting in again, building a Cluster Configuration Tool to provision large database clusters far more easily than is possible today and a few simple utilities for generating passwords, histograms, and for testing disk subsystems.