I've found the assortment packs from Rockler to be very good quality
screws, and actually to be cheaper than buying the individual 100-
packs.
http://www.rockler.com/product.cfm?sku=300&cs=1
These "Square-X" screws will drive with either a phillips (everyone
has one) or a square drive (works much better) bit. This combo pack
is only available online. Rockler are the only tapered head wood
screws I use now - don't bother with wood screws from Home Depot -
they're awful. One time I thought I'd save time by getting screws
there, and I twisted several heads off #10 screws. Waste of time and
money. And I haven't tried them, but McFeeley's wood screws are
supposed to be top of the line. They have combo packs also.

As far as countersinking, I have two suggestions: First, the Dewalt
tapered countersink bits (DW2567, DW2568) are the best ones I've tried
(better than Fuller or off-brands). These are available at Amazon and
my local TrueValue. Sometimes they go on sale at Amazon for about
$6.
http://www.amazon.com/exec/obidos/tg...X0DER&v=glance
Second, If you want a separate countersink bit, which is sometimes
handy, I've found this type by Lee Valley to work very well. Easy to
use, cuts cleanly. http://www.leevalley.com/hardware/pa...=3,41306,41328
I just got one of these a couple weeks ago, and it's already earned a
permanent spot within easy reach by my bench. The Weldon brand
version of these countersinks is supposed to be top notch.

Hope this helps,
Andy