Of course newegg has ethernet cables. Here is a 25 foot cable for $3.25. If you want bulk ethernet cable, check out compgeeks.com; they usually have a 1000-foot box for around $40, and it usually comes with a crimper and some rj-45 connectors.
7ft crossover cable? How about making any length straight-through cable a crossover cable. Just make a 1-2 inch adapter with one end being male another being female with one end being T-568A color code and the other T-568B color code. Or you can just got to thinkgeek.com and buy a few for $6 a each - http://www.thinkgeek.com/gadgets/tools/7470/
Because I needed a bunch of them for my lab, and when I can get cables for cheap enough, its not worth my time or effort to manufacture a bunch of them. If I just needed one, or I needed a custom lenth, I make them myself.
A crossover cable just crosses the wiring so that the TX pair on one end connect to the RX pair on the other, and vice versa. It's used when you're not using a hub or a switch, which would do this crossover for you.
CAT = Category. These days, ethernet typically uses CAT 5, 5e, or 6 cable.