Firewire/i.Link - Cables, Adapters, Cards, Hubs, Extenders and Drive Enclosures

i.link / Firewire / IEEE1394 Don't be confused.....
"Firewire" is what Apple* calls it, "i.link" is what Sony calls it. It is commonly called "DV" by camcorder manufacturers. IEEE-1394 is the name of the IEEE standard.
As far as cables are concerned, you really just need to worry about matching up connectors. There are three connectors: 4-pin, 6-pin and 9-pin. Laptops and Camcorders usually use the tiny 4-pin connector. Desktop Pc's and Macs use 6-pin or if they are newer maybe 9-pin. The 9pin is for 1394b which supports up to 800Mbps, as opposed to the 400Mbps maximum of 1394a.
More Info:
DVI/HDMI/1394 Home Theater Connection FAQ
IEEE-1394/Firewire/iLink card installation problems

There are basically two types of Firewire and three types of connectors to be concerned about. Unfortunately before we get to them, we really should mention all the names people use for it. IEEE-1394 is the IEEE Standard specification, or we should say IEEE-1394a and IEEE-1394b are the standards.
Firewire is Apples name for it,and since they developed it, that is what it is usually called. i.Link, is Sonys name for it.
DV is another general term associated with it.
Firewire 400 | 1394a
Also called i.link or DV, you get almost 400mbps as a top speed, but cable lengths are limited to about 15 feet. There are two connectors, a small 4-pin and a larger 6-pin connector. The 4-pin does not have power connections, so peripherals cannot be cable-powered, they must have their own power supply.

Firewire 800 | 1394b
Firewire 800 operates at a maximum of almost 800Mbps (100MBps!) and uses a 9-pin Connector. Cable lengths can be much longer than Firewire 400 (IEEE1394a) and Fiber Optic systems can run up to 100 meters.
Connection FAQ:
A) You Cannot connect Firewire to USB. Get over it. Really, we're very Sorry...
B) Connecting a 9-pin 1394b connection to a 6-pin or 4-pin connection at any point means you have a 1394a connection. You cannot have 800Mbps, sorry.
C) Camcorders usually have 4-pin connections, as do many laptops and most smaller devices. Desktop Computers have 6-pin or sometimes 9-pin connectors. Portable drives have 6-pin or 9-pin connectors as well, except the little 2.5" drive ones which often have 4-pin.
D) You must have some sort of firewire on your computer to connect to a Firewire device. These must connect through a slot - PCI, PCMCIA or higher slots.
Converters for parallel ports, serial ports, or yes, again USB, do not exist!