divine will use ARP requests to look for hosts that are always up in the networks that you frequently use your laptop in and then set the IP configuration including /etc/resolv.conf and write proxy settings in /etc/proxy. A perl script to edit your netscape 4 preferences is included. You can also run a custom script for each network to edit /etc/printcap or /etc/issue or whatever you feel like. The ARP method is much quicker than the "ping" method that other solutions use.
EtherApe is a GNOME/pcap-based etherman, interman, and "tcpman" clone. It displays network activity graphically. Active hosts are shown as circles of varying size, and traffic among them is shown as lines of varying width. It supports Ethernet, FDDI, Token Ring, ISDN, PPP, WLAN, and SLIP transports. It knows about VLANs, IP, IPv6, TCP, UDP, FTP, and a number of other protocols. Additional statistics windows will let you concentrate on protocols or nodes.
Ethernet Frame Diverter is mainly used for setting up a bridge with Squid running on it and transparently caching the Web traffic between the LAN and the router. "Transparent" means that no reconfiguration of the router or the clients is required. It also means that, in case of trouble, the machine can be replaced by a simple crossover RJ45 patch cord.
Ettercap is a network sniffer/interceptor/logger for ethernet LANs. It supports active and passive dissection of many protocols (even ciphered ones, like SSH and HTTPS). Data injection in an established connection and filtering on the fly is also possible, keeping the connection synchronized. Many sniffing modes were implemented to give you a powerful and complete sniffing suite. Plugins are supported. It has the ability to check whether you are in a switched LAN or not, and to use OS fingerprints (active or passive) to let you know the geometry of the LAN.