Freshmeat is an index of software for Unix, cross-platform, and PalmOS software, with a heavy emphasis on open source and/or free software. They also index themes (see skins) for various window managers and other applications. It is part of the Open Source Development Network, Inc. ("OSDN").
Freshmeat not only provides an index of packages, but also develops their own content in the form of editorials, book reviews, and tutorials. Some of these are developed by in-house editors and others are contributed by "open source luminaries".
Registered users get a decent added feature set; You can pick which sections appear on the main page, and (perhaps even more usefully) you can choose an arbitrary font in which to display freshmeat. You can also send short messages to other freshmeat users. Finally, as a user you can subscribe to notices tracking new releases of a 'project' (or software package) or rate a project.
Oddly enough for a site which promotes open source and free software, the source code itself for "FM" (as they call the site engine) is not available.
Freshmeat is incredibly useful if you are searching for a free/open source package to get something accomplished. There are some problems with the implementation, however. For example, in the themes section, until you deliberately go to a subcategory, the site does not display what the theme is for unless that information is in the project description.
For those wondering where themes.org went, freshmeat swallowed it on May 1st, 2002, and thus gained its themes section. Even given the UI deficiencies on the site, this is definitely a boon as themes.org was extremely slow.