Coyote Linux is a mini distribution designed for setting up network utility services such as Internet connection sharing, firewalling, or wireless access points. The goal is to make it as quick and easy as possible to set up a Linux system with only a minimal amount of Linux knowledge.
fli4l is a single-floppy Linux-based ISDN/DSL/ethernet-router. It features configuration with some simple ASCII-files, several possible connection-flavors (in/out/callback, and raw IP/PPP), channel bundling (an extra channel can be added through a Windows/Unix-client), configuration of multiple networks, least-cost routing, automatic choice of provider, display/calculation of connection times and costs, and a Windows/Unix client to control dial/hangup, monitor traffic and monitor incoming calls on ISDN (see screenshot).
Pklinux-bigi is a Slackware derived distribution based on glibc 2.2 and Linux 2.4.0-test11. It can run on 386, 486, 586, and Pentium machines with only 4 MB of RAM. Builtin features include IP tunneling, firewalling, encapsulation, QOS(based on ipv4 RSVP), kernel debugging, loopback, network block device, and numerous filesystems (including ntfs and sysV). It contains Apache, proftpd, bind 9.0, syslogd, sendmail, iptables, iproute2, and gated. NAT configuration by iptables is included by default. It is a loopdisk based distribution which can be directly run from DOS, no hdd partitioning needed. This distribution is kept as minimal as possible and it can be useful in places where you want a low end computer to act as a firewall, webserver, mail server, router, or an alternative to zipslack.
Pocket Linux is an almost minimal, one floppy linux system designed to quickly convert PC workstation into secure linux-based workstation using ssh to connect to remote host (other networking clients are also supported). It supports bootp for determining host IP and other network parameters (there's also manual configuration possible, but bootp is recommended). In addition to workstations equipped with a network card (ethernet or arcnet), you can also use Pocket Linux on a PC equipped with a modem. Modem is automatically detected and then PPP connection is made.
QuickSwitch lets you switch network profiles on the fly (IP address, DNS, routes, NFS shares, etc.). There is a command-line configuration mode by which you can change your entire network setting in one line (including DNS and routing table). It is highly configurable, supports DHCP/BOOTP/NIS/NFS/etc., and also includes a curses-based GUI which you can use as a profile selector on startup.