What's the difference between .com, .net, .org domain names?

Originally, the three letter extensions after the dot (or Top Level Domain/TLD) were meant to denote whether the domain name was being used for business (.com) charity/non-profit (.org) or for a technology based company (.net). However, with the explosion of the Internet (and specifically, the world wide web) as a new business medium, the lines were blurred, and companies and individuals alike started cross-registering domains (ie. Me.com, me.net, me.org) just to protect their interests. Now, .com, .net, and .org names (the generic Top Level Domains) can be used for any purpose.