pyratemp is probably (one of) the smallest complete template-engines for Python (with about 500 LOC). It has a very small set of special syntax in the templates. This reduces complexity and the probability of bugs and lead to an easy-to-use and intuitive user-interface. It uses embedded Python-expressions (in a "sandbox"), is well documented, has full Unicode-support, and produces very good error-messages, which is very useful when creating new templates.
QuantLib is a cross-platform, quantitative finance C++ library for modeling, pricing, trading, and risk management in real-life. It is also wrapped as Python/Ruby/Scheme modules. Extensions for Excel, R, and Mathematica are available. Other such extensions are under consideration. QuantLib offers tools that are useful both for practical implementation and for advanced modeling. It features market conventions, yield curve models, solvers, PDEs, Monte Carlo (low-discrepancy included), exotic options, VAR, and so on.
Cobbler is a network installation and update server. It can be used to automatically set up PXE, install virtual guests, manage answer files, and reinstall existing Linux machines. Advanced features include importing distributions from DVDs and rsync mirrors, kickstart templating, integrated yum mirroring (integrated with the installer to make updates available at install time), creation of netboot ISOs, and built-in DHCP/DNS Management. Tools such as "cobbler triggers", a Python API, and an XMLRPC API allow integration with cobbler with the rest of your datacenter environment or other systems management applications. There is also a Web interface to simplify management of the install server. Cobbler supports RHEL 4+, Fedora, and derivative distributions, and is also able to install other popular distributions.
Scapy is a powerful interactive packet manipulation tool, packet generator, network scanner, network discovery tool, and packet sniffer. It provides classes to interactively create packets or sets of packets, manipulate them, send them over the wire, sniff other packets from the wire, match answers and replies, and more. Interaction is provided by the Python interpreter, so Python programming structures can be used (such as variables, loops, and functions). Report modules are possible and easy to make. It is intended to do about the same things as ttlscan, nmap, hping, queso, p0f, xprobe, arping, arp-sk, arpspoof, firewalk, irpas, tethereal, tcpdump, etc.
Elektra is a universal hierarchical configuration store, similar to GConf and the Windows Registry. It allows programs to read and save their configurations with a consistent API, and allows them to be aware of other applications' configurations, leveraging easy application integration. While architecturally similar to other OS registries, Elektra does not have most of the problems found in those implementations. Elektra includes a library, an API, and commandline and GUI tools for administration tasks.
mididings is a MIDI router and processor for ALSA and JACK MIDI. It supports filtering and modifying MIDI events in many different ways, and allows for seamless switching between different patches even while playing. mididings is scriptable and extensible in Python, while the core MIDI processing code is written in C++ in order to allow low latencies and realtime usage.