I've gone almost exclusively to Triumph "Thunderbits", 135 deg split points. Decent price for USA bits, and seem to hold up pretty well. I get mine through Enco, but I'm sure there are other vendors that are competitively priced. I've also heard rumors that these are the bits that are re-branded for Snap-On, and sold at a significant markup. (If anybody can verify, that would be great)
I used to like Precision Twist Drill (PTD) bits, but I've noticed lately that the replacement bits I've gotten are no longer made in the USA (mostly Brazil), and still cost more that an equivelant Triumph "Thunderbit".