I bought a pair of Planet Bike Blinky Super Flash LEDs for the rear and a Cateye HL-EL320 LED Bicycle Headlight (I also have a second older headlight). The super flash is VERY bright and completely weatherproof. The Cateye is bright enough to not just be seen, but to see where you're going (it also doubles as a great flashlight for hiking).
Retroreflectivity also never hurts, so I also got a reflective safety triangle from Adventure Cycling for the rear of the bike, and I also wear a reflective orange motorcycle vest from Conspicuity.
The biggest reason for the "extreme" visibility is that my wife and I ride in all weather, including near white-out conditions and pea-soup fog, so we need to be as absolutely visible as possible. Also, from the driver's perspective, I really appreciate when a cyclist is highly visible, and therefore you have plenty of time to slow down and drive around them. I've also found that the distance vehicles give you either on a bicycle or motorcycle is directly proportional to your visibility.
Here are some pictures of the total setup:
