Only cold process or hot process shampoo bars need lye. There are also syndet shampoo bars as well.
I've seen recipes for melt and pour shampoo bars, where really all they do is add castor oil to it. That doesn't work.
I've heard of people using Shaving Melt and Pour bases as shampoo bars (
http://www.brambleberry.com/Shaving-Mel ... P4384.aspx)
I've never tried that, but I'm sure it would be similar to a shampoo bar.
Personally, I prefer syndet shampoo bars because using MP & CP on my hair makes it feel really dry after a while.
There's alot of info on Susan's blog about syndet shampoo bars
http://swiftcraftymonkey.blogspot.com/You can also buy a kit to try your hand at making syndet shampoo bars
http://www.scentersquare.com/index.php? ... x&cPath=14