Free Resistors
A look at what is currently available on eBay
 100 x 2mm Mixed color Mini LEDs & Free Resistors #LED2 US $9.99 
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 105 X 5mm 7 Colors LED Each Color 15 pcs Free Resistors US $8.99
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 20 pcs 3mm Blue LED Lamp 8000mcd & Free Resistors US $3.99
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 20 pcs 3mm Green LED Lamp 15000mcd & Free Resistors US $3.99
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 20 pcs 3mm Red LED Lamp 15000mcd & Free Resistors US $3.99
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 20 pcs 3mm UV LED Lamp 300mcd & Free Resistors US $3.99
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 20 pcs 5mm 850nm Infrared IR LED & Free Resistor US $3.99
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 20 pcs 5mm 940nm Infrared IR LED & Free Resistor US $3.99
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 20 pcs 5mm Blue LED Lamp 8000mcd & Free Resistors US $3.99
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 20x Ultra Violet UV 2x5x7mm Rectangle LED Free Resistor US $.99
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 Lot of 100 X 5mm Blue LED Lamps 8000mcd Free Resistors US $2.99
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 15x 5mm Yellow Blink Flash LED Bulb Free Resistor US $.99
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How do I rig up some LED lights to a battery source and switch?
I want to put some LED lights into something. Basically I just want the lights to run on battery power (AA, AAA, or 9V), and have either a toggle or momentary switch to turn them on/off (haven't decided yet). I have essentially no electrical experience.
I have ordered the LEDs themselves. They also come with free resistors (it says they "work for 12v"). What other items do I need, and how do I put this together? Will a soldering iron be required?
Here some of the LED specifications:
Emitted Colour : Ultra Violet UV
Size (mm) : 5mm ( Flat Top )
Lens Colour : Water Clear
Peak Wave Length (nm) : 405 ~ 410
Forward Voltage (V) : 3.2 ~ 3.6
Reverse Current (uA) : <= 30
Luminous Intensity Typ Iv (mcd) : 2000
Viewing Angle : 85 ~ 100 Degree
Gosh! that's too much specifications for a simple battery powered LED indicator with a switch. The specifications are required when you are designing serious circuits. Don't worry about them for now.
If the company provides you with resistors you don't have to then worry about calculations. You could connect the LEDs in series or in parallel (series helps in dropping voltage current flowing remaining constant, parallel helps in same voltage fed, current varying depending on consumption of each LED). Resistors are used to limit current. A switch is always in series from the battery (a device used in place of breaking or making a connection).
You may need a soldering gun with lead and flux as well as a cutter and nose plier to put them in order. (LEDs have polarities like batteries). It is safe to work on 3 V inputs and making connections, nothing goes wrong with these devices even if you connect them in reverse (only they don't work). ONLY IT IS IMPORTANT YOU DON'T DIRECTLY SHORT THE external LEADS OF THE BATTERY.
Use Ohm's law that is very simple to check the current limit and voltage drop by the LED. Resistor in Ohms equals Voltage in volts divided by current in amperes. Use algebra to manipulate: R=E/I. It does help if you have a soldering iron and a cutter and a nose plier.
