Zfswatcher is ZFS storage pool monitoring and notification daemon. It periodically inspects the zpool status and sends configurable notifications on status changes such as disk failures. It also controls the disk enclosure LEDs. There is an embedded Web interface for displaying status and logs.
cola is a C implementation of the COLA structure described in the paper "Cache Oblivious Streaming B-Trees" by Bender, Farach-Colton, et al. This algorithm is a drop-in replacement for B-Tree databases/indexes which performs faster on spinning disks than B-Trees do on SSD. It's asymptotically optimal in terms of data transfers to and from disk. For example, random key inserts are turned into linear sequential writes while maintaining the property which queries always require, at most, precisely log N blocks read sequentially (but not contiguously) from disk (or half that, on average).
ashttpd was originally a testbed for a kernel async-sendfile patch. Today, it's just another Web server for serving static content rapidly. It differs from its competitors by storing its webroot in a database, which provides a 50% performance increase over using the operating system's VFS. It also allows precalculation of strong cache-validators (ETags).
Archivist is a network device configuration archiving and versioning program. It uses Subversion as its revision control system. Its multithreaded design makes it quite fast and thus suitable for operation on large networks with thousands of network devices. It supports Cisco IOS, Cisco CatOS, Juniper JUNOS, and Brocade/Foundry MLX series, but it can be easily extended to support any SSH or telnet-based network device by creating your own config download and post-processing scripts.