Do I need to buy a special stand for my front wheel when using my turbo trainer? I have seen available special "stands" (please tell me the correct terminology) to be placed under the front wheel when using a turbo trainer.

I normally just put a copy of the phone directory down on the floor, opened in the middle to hold the wheel in place.

Should I lash out and buy one of the specialised devices?
A nice advantage of the specialized stand is that it will keep your front wheel pointed front. So you won't have to expend energy keeping it that way. A brick or telephone directory (or anything that's just level and the right height) won't do that.

A piece of wooden plank will, after you hack away at it with an axe a few times right in the middle. If you're looking to save $20 it's the perfect solution.