If you have studded walls (plasterboard on wooden frames) the boxes that are flush are called pattress boxes. There is a different box for sinking into brick walls. Both types can take yet another type of box screwed on top if you want but it's not as neat. All the boxes will then take the same fascia plates and there are a variety to choose from (single plate, modular, multi, etc)
I've got the floorboards up to check the joists ATM so I'm taking advantage of this to wire up my house. I'm putting Cat 5e cable in, which I bought a few years ago, although I do wonder whether I should have put Cat 6 as this will be a future standard. I'm putting a telephone cable in at the same time (also previously bought) although this is less important now with cordless phones. I'm also putting in cables for satellite/TV at the same time.