Axibase Time Series Database - ATSD is purpose-built for analyzing and reporting on massive volumes of time-series data collected...
KX - Kx Systems has a high-performance vector database, kdb+, with a built-in programming language, q, that sets the standard for time-series analytics.
OpenTSDB - OpenTSDB is a distributed, scalable Time Series Database (TSDB) written on top of HBase.
Thomson Reuters Datastream - Thomson Reuters Datastream is a financial time series database that allows to identify and examine trends, generate and test ideas and develop view points on the market.
RRDTool - High performance data logging and graphing system for time series data
InfluxData - Scalable datastore for metrics, events, and real-time analytics.