New memcache client / updated old memcache client
It's a sad truth that many good and relatively popular open source projects die a slow death because they lose there maintainers and nobody steps up to replace them. One example would be PHPEclipse, a remarkebly stable and feature rich PHP plugin for Eclipse. For the longest time, it was leaps and bounds above PDT, the "official" PHP plugin. (PHPEclipse has recently been revived) The issue is only exacerbated if language the project is written in is unfamiliar to its user base. Eclipse plugin development (Java) is a huge leap even for a professional PHP developer.
This sort of problem strikes far less often when the project in question plays an important part in a successful company, since they have the resources to pay someone to contribute/maintain. It's not a guarantee though. Memcache is an excellent example. It was developed by Danga for internal use in Livejournal. It was later made public and quickly became intensely popular. The server part is in pretty good shape, although there are only about 2 releases a year. Facebook is contributing heavily now, though. Hopefully, we will see the benefits of those contributions soon.
The client library is another matter. Development there has been pretty anemic, probably coinciding with Dango's aquisition by six apart (just a guess). The C library libmemcache which serves as the underlying implementation for the higher-level language specific libraries is not being maintained anymore. The perl library has seen no update in almost 2 years. The other script languages seem to be doing better. Even PHP, which PEAR/PECL projects often suffer from abandonment issues, has been steadily maintaining their client library and even has a new major release in beta right now.
Even so, the underlying problem remains that libmemcache is dead. From digg's technology blog I now hear that not only is there a new C client library under heavy development (libmemcached), but they also hired a PHP developer to work on a new PECL extension that utilizes the new library. This is excellent news and should give memcache's client side a much needed boost to go along with the upcoming server side improvements.