Ok, regular incandescent’s run about 8 lumens per watt, halogen run about 12-15 lumens per watt, cold cathode and LED's typically run about 25 lumens per watt, HID run about 30 lumens per watt, fluorescent’s run about 40 lumens per watt and finally low pressure sodium (orangish street lights) run about 120 lumens per watt.
There are variables in all of these, they recently released a 5 watt LED running about 50 lumens per watt and I also saw a prototype 100w die running about 45%, very nice
I have a pretty good inside lead to some of the manufactures and haven't heard of any production LED's over 50 lumens per watt, yet...
One of the neat things about LED's is as the voltage is lowered (thus reducing overall power) to the LED the lumens per watt actually goes up, while halogen and incandescent lamps the lumens per watt drops WAY off. So running a halogen lamp at 50% of its rated wattage will get you about 10% of the light output and running an LED at 50% of its rated wattage will typically net you about 60% of rated light output.
A lumen is a measurement of the total light output.
If you want to know more about LED’s and or flashlights check out
http://candlepowerforums.com/ I happen to be an admin over there.