http://www.cableforum.co.uk/board/94...em-router.html may help clarify what goes where in a network.
Since most routers, wired or wireless, contain at least a 4 port LAN side switch, you don't need to add another switch or hub to your network unless you need more ports, or perhaps you have a number of bits of kit in one room remote from the router and wish to save on the numbers of wires being run.
For the cost involved, if buying a switch, I'd certainly consider gigabit speed operability. Yes it might be rare you'd benefit, especially if most LAN traffic is running via a 10/100 limited router switch, but it would offer some future proofing.