DBIx::Password provides an abstraction layer for password maintenance. It is database independent and only overrides the connect method (so it basically behaves as DBI normally does). You provide a single virtual user name in the connect method and the module determines which database/which user/which password to provide.
Gearmand is the job server component of Gearman. Gearman provides a generic framework to farm out work to other machines, dispatching function calls to machines that are better suited to do work, to do work in parallel, to balance the load of processing, or to call functions between languages.
libmemcached is a C client library for interfacing to a memcached server. It has been designed to be light on memory usage, thread safe and to provide full access to server side methods. It also implements several command line tools: memcat, memflush, memrm, memstat, and memslap (for load generation). The library has been designed to allow for different hashing methods on keys, partitioning by keys, and to use consistent hashing for distribution.
mod_filter allows you to filter output from other modules inside of Apache. This allows you to implement filters (think Swedish Chef, jive, etc.). You can also use it to retailer output for your locale. This works with HTML documents, mod_perl, PHP, JServ, CGIs, and for that matter just about any sort of custom handler you might have.
mod_layout is an Apache module that provides both a Footer and Header directive to automagically include output from other URIs at the beginning and ending of a Web page. It can be used to wrap documents for a standard look and feel for a site (or to insert banners on any given document in a site). Currently known to support mod_perl, PHP and Apache JServ. Should support just about any type of handler.