Open source projects that we've worked on here at NorthScale include moxi (a memcached proxy) and libconflate. We've also created and/or contributed to memcached, spymemcached, git, strophe and more.
moxi is a memcached proxy that we wrote to keep the memcached contract whole in complicated deployment environments. It also brings several optimizations to memcached users without requiring any changes to the application software using memcached.
memcached Amazon Machine Images for EC2 are available pre-packaged and tested. While not a separate project, we thought EC2 would benefit from having the Open Source memcached available in a simple AMI. We have also created some AMIs which have additional tools which may be useful at both development and deployment time.
libconflate is a generalized, XMPP-based, embeddable agent, written in C, and is designed to enable remote, on-the-fly configuration, reconfiguration and control of distributed processes.