Fairly obviously you need a wifi connected printer. Without that you're not going to get far. You can use just about any old printer connected to a Linux box but the setup may be a bit tedious for some. Other than that a printer attached to a Mac attached to a network attached to WiFi.
In Safari you then select "print" which is on the same menu as "mail" and "tweet". when you select print you get a dialogue that lets you select which printer and the number of copies.
It's all considerably easier if you have an AirPrint capable printer which iirc is most of the consumer models. It's well summarised here: