Almost all recent laptops are equipped with a built-in network card. This chapter shows some methods to connect older laptops without internal network cards.
If your laptop supports PCMCIA this is the easiest and fastest way to get network support. Make sure your card is supported before buying one.
Probably the cheapest way to connect your laptop to another computer, but quite slow. You may use PPP or SLIP to start the connection.
Accton Pocket Ethernet and Linux This ethernet adaptor uses a parallel port and delivers approximately 110k Bytes/s throughput for those notebooks that do not have PCMCIA slots.
Offers more speed than a serial connection. Some laptops use chipsets that will not work with PLIP. Please see PLIP-HOWTO for details.
Wake-On-LAN works with some laptops equipped with built-in network cards. Wake-On-LAN is the generic name for the AMD "Magic Packet" technology. It's very similar to the PCMCIA modem "wake on ring" signal line. The basic idea is that the network adapter has a very-low-power mode to monitor the network for special packet data that will wake up the machine. The etherwake package as well as the Wakeonlan Perl script are able to send 'magic packets' to wake-on-LAN enabled ethernet adapters and motherboards, in order to switch on remote computers. You may use ethtool to configure some special Wake-On-LAN settings.