Alkaline is a full-featured standalone search and index server. The spider is a fully remote indexing daemon which includes support for all standards like robots.txt and "skip" meta tags, and allows multiple distinct configurations and search groups (searching many different sites from your server), including complex regexp indexing paths, authentification, filters for various document formats, XML-based online management and statistics, mrtg-compatible perf numbers, and more.
auth_ldap is an LDAP authentication module for the Apache Web server. Auth_ldap has excellent performance, due to its use of aggressive client-side caching algorithms. It also has support for LDAP over SS or TLSL. It also features a mode that lets Microsoft Frontpage clients manage their Web permissions while still using LDAP for authentication.
Boa is a single-tasking HTTP server. That means that unlike traditional Web servers, it does not fork for each incoming connection, nor does it fork many copies of itself to handle multiple connections. It internally multiplexes all of the ongoing HTTP connections, and forks only for CGI programs (which must be separate processes), automatic directory generation, and automatic file gunzipping. Tests show boa is capable of handling up to several hundred hits per second on a 100 Mhz Pentium, dozens of hits per second on a lowly 20 MHz 386/SX, and thousands on more powerful CPUs.
ctm.pl is a Perl script which generates Apache type maps for use with mod_negotiation. Useful if you have a lot of images available in different formats you need type maps for, especially if you don't want to use MultiViews to decide which of them will be sent back to the requesting browser.