asdf-config
(DEPRECATED, July 2006: This functionality was recently superseded by Gary King's new asdf operation 'load-preferences' - it provides a slightly different and more general variant of the variable initialization support of asdf-config)

asdf-config is an ASDF-extension that enables easy user configuration and automatic initialization of asdf packages without requiring source edits.

asdf-config provides two new commands configure-op and initialize-op. configure-op keeps a registry of key-value pairs that initializes a variable after load-op completes. initialize-op depends on configure-op and will call a special package init function to, for instance, load data from a data directory after installation.

A single asdf-config source file can be downloaded from http://web.media.mit.edu/~eslick/asdf-ext/

At some point I'll make this asdf-installable