Potion: A bash based provisioning template, like puppet, but smaller and faster.
Drove: modern monitoring tool which support alerting (with escalation), auto-register nodes, statistics gathering and much more in a few lines of python code.
Dtools: Bash based paralell distributed tool, similar to paralell ssh, but with more features and cloud integrations.
Libcalby: C library to manage different time events, calendars and time formats.
Libnss_map: NSS library written in C to map different users to the same UID, to implement authentication described in paper 2011/06031.
Pyload: Tool to create self-executable python applications in a binary static-linked executable, as described in paper 2015/09101.
Nfs3_failover: Set of patches for mount utils and linux kernel 2.6 to add automatic failover to NFS3 mountpoints.
Mole: Log analytic system in command line, designed to parse and query tons of logs from the terminal.
Whistler: Modular XMPP bot written in python.
Mico: Tool to define server infrastructure programatically for the cloud, as proposed in paper 2013/03141.
collectd: System metrics collection system designed and implemented by Florian Foster
HiPack: Serialization protocol designed to be human-readable and easy to be proceesed by a machine, designed by Adrián Pérez
Sometimes I think about computer science and write some papers. You can see the collection here.