RJ-45 Connectors - Patch Cords for Category 5 Wire

Standard Patch Cord
(use this on both ends of a normal patch cord)
Cross-over Cable
(use this on one end of a cross-over cable)

Straight-Through vs Cross-Over
In general, the patch cords that you use with your Ethernet connections are "straight-through", which means that pin 1 of the plug on one end is connected to pin 1 of the plug on the other end. Voice cables are "crossed" end to end; data cables aren't.

The only time you cross connections in 10BaseT is when you connect two Ethernet devices directly together without a hub. This can be two computers connected without a hub, or two hubs via standard ethernet ports in the hubs. Then you need a "cross-over" patch cable, which crosses the transmit and receive pairs, the orange and green pairs in normal wiring. In a cross-over cable, one end is normal, and the other end has the cross-over configuration.

More Standards
A good FAQ on cabling standards is at Ohio State