Part of the problem is that people don't agree. And when you're arguing about why yours is better, the buzzwords tend to come out.

But my advice?

http://www.dealextreme.com/details.dx/sku.13060 Light, $34.16
http://www.dealextreme.com/details.dx/sku.5790 Batteries, 2 for $8.18
http://www.dealextreme.com/details.dx/sku.8274 Mount, $1.54 (get one for each bike)
http://www.dealextreme.com/details.dx/sku.1251 Charger, $12.30
http://www.dealextreme.com/details.dx/sku.18307 Backup light, $7.43

Total: $63.61 (no tax, shipping is free, but takes about a month), plus you'll need 4 AAA batteries for the backup light. Being that it's a backup, alkalines should be fine -- it shouldn't be used much.

This will give you a really bright light that will last 8 hours if you use in low mode, or about 90 minutes in high mode. However, this light is a bit fragile, so I also suggest getting the backup light. (I've had things vibrate loose inside, but it's never broken so badly that I couldn't fix it in a few minutes.) I'm serious about the brightness -- other cyclists will be amazed at how much light you've got, unless they 1) have about the same thing or 2) spent hundreds of dollars on something else.

Here's a cheaper charger --

http://www.dealextreme.com/details.dx/sku.22576 Charger, $4.39

But I've not tried this one. If you must be under $50, you can get there by getting the cheaper charger and skipping the backup light. But I'd suggest having the backup light.

The backup light is pretty impressive for what it is -- pretty well made for the price (unlike many of the DealExtreme lights), puts out a decent amount of light. The first light is still much brighter, but the backup light is adequate.

If you're on a smaller budget, get two of the backup lights (skip the other stuff) along with 8 - 16 rechargeable AAA batteries and a charger. Aim one light a bit ahead of your front tire, and the other light further ahead.

i.e. get this --

http://www.dealextreme.com/details.dx/sku.18307 Light, $7.43, buy two of them.
http://www.dealextreme.com/details.dx/sku.72 AAA batteries, $2.39, buy four packs.
http://www.dealextreme.com/details.dx/sku.29177 Charger, $5.99

... for a total of $30.41. You can save a few bucks by not buying the spare batteries, but it's nice to have a full set of spares, so you're never waiting for batteries to charge.

If you need a rear light, I'm pretty happy with this --

http://www.dealextreme.com/details.dx/sku.3639 red tail light, $3.67

EDIT: updated because I was wrong about the batteries used by the backup light.