Grr, I just typed a reply and made a mistake and now it's gone :S
Cable wise, go for Cat6 or better. Cat6 handles gigabit speeds better, and is expected to reach 10Gb speeds. May not seem like a major issue now, but that's what people thought about 10Mb cabling 10 years ago. All in all, won't cost you more than 50$ extra to do Cat6, as it's became the standard for new cabling.
Switch wise, look for a decent 16+ port switch. I'd get one with at least gigabit uplinks. Something like this would be ideal, I've had two running for two years with only one crash
http://www.newegg.com/Product/Product.aspx?Item=N82E16833127222 The gigabit capability's really add alot of potential, as well as the ability to have add in cards to handle fiber links. Actually has some brains, so it can monitor itself for problems too and even report them. Many of the other features can come in real helpful like QOS and VLAN's, and it supports 802.1X which is the future of network security. Cheaper switches can erm, die when under heavy loads quite easily.
Router wise, you're going to want something beefy and not a consumer router like they sell at best buy. Not even some router running tomato or DD-WRT will suffice. What router to buy will depend on what you want to do with it. If your confident on doing something yourself, a small linux distribution called smoothwall will do nicely and offer you extreme performance and reliability (if the hardware you install it on is reliable) for the price of an old p3 era PC.
And make sure you have a decent "modem" if your running DSL / Cable. The crap your ISP gives you likely won't suffice.
