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.
DeleGate is a multi-purpose application level gateway or proxy server that mediates communication of various protocols, applying cache and conversion for mediated data, controlling access from clients, and routing toward servers. It translates protocols between clients and servers, converting between IPv4 and IPv6, applying SSL (TLS) to arbitrary protocols, merging several servers into a single server view with aliasing and filtering. It can be used as a simple origin server for some protocols (HTTP, FTP, and NNTP).
fhttpd is an FTP/HTTP server with modules support. Modules run as separate "looping" processes locally or remotely, and can be configured to run under separate userids. Locally running modules can be configured to use fd passing of client's connection to avoid overhead in sending the response. ~username URL to directory remapping is supported in HTTP, and can be configured to access files, run scripts and modules under mapped user's userid.