RF Local Area Networks / WiFi

Wifi 802.11 is the current standard for wireless networking.

Features of 802.11 Radio

STBC (Space-Time Block Code) xmits multiple copies of data at different times and using different antennas in order to supply combinations that work best thus increasing reliability. ^
MIMO (Multiple Input Multiple Output) uses multiple antennas to compensate for and expliot signals taking more than one path from station to station. It is an essential part of 802.11n/ac Wifi. ^

Mark Willis said (many years ago):

Panasonic makes a cordless brick-sized "cordless modem phone" deal,
limited to 33.6k baud IIRC;  I have one, can get the part number if you
want.

There also are a number of wireless NICs in PCMCIA, ISA, PCI, and
Parallel Port formats, at varying prices (From 800kbps to lots faster
for more $$$);

IBM "Wireless LAN Entry" lines, either the 8227 or 92G7787, or the
80G0900 or 80G1000; About $40ish per NIC;  see
http://www.networking.ibm.com/wireles/wdprods/jb.htm,
http://www.fivepoints.net/ibmwireless.html,
http://www.networking.ibm.com/wireles/wdprods/jb.htm,
http://www.networking.ibm.com/wirenew/wdprods/ge.htm#lanentry,
http://www1.s390.ibm.com/bookmgr-cgi/bookmgr.cmd/Shelves/E2S0BK01,
http://publib.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/SG244466/CCONTENTS,
http://www.crisp.demon.co.uk/wireless.html for Linux driver)

AeroComm makes something in this line IIRC.  So do many other companies.

Linux and Wireless LANs:
http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/

Wireless LAN from Laptop to a desktop (or other Laptop) on the LAN,
another machine on the LAN has a modem / DSL / Cable Modem connection to
the Internet;  You run IPRoute, WinGate, a Linux Router, or a Gnat Box
to cross-connect these (Among others!):
http://www.mischler.com/ for IPRoute
http://projects.shn.nu/homenetwork/iproute/index.shtml
http://www.linuxrouter.org/
http://lrp.c0wz.com/
http://www.gnatbox.com/
http://www.wingate.com/