The recipe listed above ccunning is what I know as a simple white sauce. The Bechamel recipe that I was taught is almost identical, barring the fact that the milk used should be infused first.
This is done by adding half an onion, a bay leaf, 3-4 black peppercorns, half a chopped carrot, half a chopped stick of celery, and (depending on the slightly different versions of this recipe out there) a blade of mace, to the milk. This mixture is then heated to just below boiling point, before letting it cool, and straining it. You then use it just as in ccunning's recipe, but make sure you cook the resulting sauce through for around 20 minutes, to break down the starches in the flour otherwise it will taste the sauce.
The result is a more savoury sauce with more depth of flavour.