Brake Fluid I use Castrol and get it at Pep Boys
Oil I get where ever I get the best deal on Rotella, lately at walmart
Oil filters I get at Great American trucks parts, they carry Wix which are very good and the oil filters are only about $4.50. (Also sold at NAPA for a $1 or 2 more)
Until I see some actual evidence that OEM is better, I'll continue to get Wix air filters at NAPA.
Plugs I get whoever has them cheapest
Wires I get from Kingsborne, good quality for good price.
Belts Gates or Goodyear or the like locally for whoever has them on sale.