vded is a simple REST-type method for tracking deltas of ever-increasing values (although it handles resets, etc., pretty well). It is meant to accept submissions of values which increment, then determine the delta between that value and its predecessor, as well as figure the rate over time.
Chief Database records time series data in real time. Data is compressed to reduce disk requirements and improve performance. Redo logging and caching provide high performance on minimal hardware, with minimal data loss in the event of hardware failure. 1 million coordinates can be processed per second on server-level hardware. All interfaces are SOAP; allowing for easy integration with other systems and Web sites. Data is usually from a telemetered resource, but can also come from SNMP. Chief Trends allows for trending data inside Firefox. Chief Calculator is a Perl calculation engine to manipulate the data in whatever way you want.