Libxml2 is the XML C library developed for the Gnome project. The library code is portable (to Linux, Unix, Windows, embedded systems, etc.) and modular; most of the extensions can be compiled out. Libxml2 implements a number of existing standards related to markup languages, including the XML standard, Namespaces in XML, XML Base, Relax NG, RFC 2396, XPath, XPointer, HTML4, XInclude, SGML Catalogs, and XML Catalogs. In most cases, libxml tries to implement the specifications in a relatively strict way. To some extent, it provides support for the following specifications, but doesn't claim to implement them: DOM, FTP client, HTTP client, and SAX2. Support for W3C XML Schemas is in progress. It includes xmllint, a command line XML validator.
BitTorrent is a tool for copying files from one machine to another. FTP punishes sites for being popular. Since all uploading is done from one place, a popular site needs big iron and big bandwidth. With BitTorrent, clients automatically mirror files they download, making the publisher's burden almost nothing.
GraphicsMagick is a robust collection of tools and libraries which support reading, writing, and manipulating an image in over 90 major formats including popular formats like DPX, DICOM, BMP, GIF, JPEG, JPEG-2000, PDF, PNG, PNM, SVG, and TIFF. A high-quality 2D renderer is included, which provides a subset of SVG capabilities. C, C++, Perl, Tcl, and Ruby are supported. Originally based on ImageMagick, GraphicsMagick focuses on performance, minimizing bugs, and providing stable APIs and ABIs. It runs on all modern variants of Unix, Windows, and Mac OS X.
Dosage is designed to keep a local copy of specific Web comics and other picture-based content such as Picture of the Day sites. With the dosage command line, script you can get the latest strip of a Web comic, catch up to the last strip downloaded, or download a strip for a particular date/index (if the comic's site layout makes this possible).
Libxslt is a C library for GNOME which allows developers to work with XSLT. It is based on libxml for XML parsing, tree manipulation, and XPath support. Also included is 'xsltproc', a command line XSLT processor. The library is written in plain C, making as few assumptions as possible, and sticking closely to ANSI C/POSIX for easy embedding. It should work on Linux, Unix, and Windows. Though not designed primarily with performances in mind, libxslt seems to be a relatively fast processor. It also include full support for the EXSLT set of extension functions as well as some common extensions present in other XSLT engines.
Twisted is an event-based framework for Internet applications. It includes a Web server, an SMTP/POP3 server, a telnet server, an SSH server, an IRC server, a DNS server, a generic client/server pair for remote object access (Perspective Broker), and APIs for creating new protocols. It supports integration with GTK+, GTK+ 2, Qt, Tkinter, wxPython, Mac OS X (PyObjC) and Win32 event loops. It also supports TCP, SSL and TLS, UDP, Unix sockets, multicast, and serial ports. Supported protocols include HTTP, FTP, SMTP, POP3, IMAP, TOC, OSCAR (AIM and ICQ), SSH, DNS, IRC, NNTP, Jabber, SOCKSv4, Telnet, SIP (for VoIP), and XML-RPC and SOAP using external packages. Most protocols are supported as both servers and clients.
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.
SCons is a software construction tool (build tool substitute for Make) implemented in Python. It features a modular build engine that can be embedded in other software. SCons configuration files are Python scripts that call the build engine API. It can scan files to detect dependencies automatically and maintain a global view of all dependencies in a build tree, and uses MD5 signatures to detect changed file contents reliably. Timestamps can be used if you prefer. SCons also supports parallel builds and is easily extensible through user-defined builder and scanner objects.
Submin provides a Web-based admin interface to your Subversion and Git repositories. Its features include user/group management, path permission management, the ability to create svn repositories and managing commit email messages. For Subversion, authentication is done with htpasswd/svn authz, so it can use the same login information as apache2/svn (and trac). For Git, ssh is used, and the login information is synched whenever a change is made. The Web interface can also work with NGINX/uWSGI, but the Subversion part only works with Apache.