Well, what is the ethernet cable coming from and what 2 devices is it going to?
You're answer really depends on more detail.
In general, you'd be better off just using a small switch or a hub. But, sure... you could literally just split the cable up to connect to 2 devices... sure.
In order to split the connection yourself, you would need a couple of female ends and then a couple of additional cables. In all reality, whatever device it's coming from thinks that it is also talking to one device ... so, "spitting it" really wouldn't work unless you actually split it on both ends and use 1 physical cable to use on 2 devices or ports on either end.
You could actually make it fairly neat looking... but it's not going to be as clean and function as well as a switch would. They make itty bitty switches too
EDIT: (Whew.... found a picture of what I'm talking about... thought that I was going to have to fire up Visio there for a second...)
Ok, this is exactly what I'm talking about:
Cyberguys.com - Network Pair Splitter 10/100 2 Pack
You have to use it in pairs.
So, you connect two computers at one end.. then 2 ports at the other end.
^^ Perfect example.