There's a campsite opposite the Vaynol Arms in Nant Peris, the pub also has a bunkhouse and reasonable B&B and does decent beer...
There's the Youth Hostel at the top of the pass that's good for a base for doing the pyg track, or the crib coch routes to the top of snowdon, or the route over llywed
In the Ogwen valley there are a couple of campsites, and a number of barns, good for tryfan and the glydars, or the carneddau, there's an alright youth hostel at ogwen cottage...
There's another youth hostel at capel curig and there's three good pubs and a campsite by the river...