UTP category 5 cable, sometimes referred to as simply UTP Cat5 Cable, is the current standard that is well in place for over a dozen years when it comes to network interconnecting. It's a great compromise of quality and capacity at a reasonable price, hence why it's widely used in most corporations of any size as means to have a good network access without too much congestion.
These days wireless solutions, particularly with the 802.11n draft starting to install itself on the market, starts to sound a good solution for intranet networking solutions. This may be functional to a certain degree with it comes to a handful of computers, but, as the number of machines in the network rise in number this will inevitably lead to congestion in the traffic and rather than a boost in efficiency you'll have a penalty.
UTO cat5 cabling is made to function perfectly between the interconnected devices up to distances of 100 meters (approximately 328 feet) while using a constant bandwidth of 100 Mbps. This allows for a good amount of speed without any signal break up, the only possible traffic jam being created by slow switch devices that should be upgraded in accordance to the planned network size.
A cat 5 UTP cable is constituted of 4 pairs of copper wire which are responsible for delivering this kind of speed on such a cheap cable, however, the copper wire is thin so it's typically one of the reasons for problems. Given the amount of tension that can be created on the cables physically, both due to any cable bending along with usage itself, it's not unheard of that the wires may break and require replacement of the cable altogether.
Also, there's a difference between the usual UTP cat5e cable and the UTP cat5 crossover cable. The first one is meant to link together devices like a computer and a router, whereas the crossover one is meant to interconnect two computers directly. This is important to have in mind because, while many routers have a feature that allows them to adjust to cross-over cables, computers do not.
Although at the moment UTP cat5e is still a standard, with the deployment of cat6 cable the life of cat5 may be on the end. Slowly devices are being upgraded to support Gigabit Ethernet which will require usage of the new cable and given the speed boost is that by 10 times more, the impact will be very noticeable.