This is a great article by Bruce Eckel in which he attempts to define “Consulting”.

http://www.artima.com/weblogs/viewpost.jsp?thread=122020

“I think consulting is when you have some kind of special expertise -- come by through hard struggle and learning -- that you transfer to a group of people, in a relatively short period of time, and in a way that is unique for that group. I also think that consulting involves addressing particular issues faced by that group. “

I've always tried to educate people on the difference between consulting and contracting.  I tend to agree with Bruce when it comes to the definition of consulting.  Contracting, on the other hand (and in my honest opinion), is nothing more than putting a body in a seat to do something like write code.  We've got two contractors where I work.  They may think of themselves as consultants, but they certainly don't bring any special expertise to the table...in fact, it seems like I'm constantly schooling them on things I believe they should already know. :-)