Update 2: The folks at Hypertable would like you to know that Hypertable is now officially sponsored by Baidu, China’s Leading Search Engine. As a sponsor of Hypertable, Baidu has committed an industrious team of engineers, numerous servers, and support resources to improve the quality and development of the open source technology.
Update: InfoQ interview on Hypertable Lead Discusses Hadoop and Distributed Databases. Hypertable differs from HBase in that it is a higher performance implementation of Bigtable.
Skrentablog gives the heads up on Hypertable, Zvents' open-source BigTable clone. It's written in C++ and can run on top of either HDFS or KFS. Performance looks encouraging at 28M rows of data inserted at a per-node write rate of 7mb/sec.