A chance encounter with a 100-pack of green LEDs inspired my daughter and me to make an wreath totally out of LEDs. We wound up using 96 of the green ones, plus 5 red LEDs left over from a previous flea market visit, for a total of 101 LEDs.
It can be twisted together without tools, but soldering makes it sturdier and a pair of needle-nosed pliers and a third hand jig will make it easier.
ROHS LEDs (about a dollar more per pack) and lead-free solder is always an option, or just wash your hands and don't stick your fingers in your mouth.
Step 1: Parts and Tools Required
100 Green LEDs
5 Red LEDs
A few feet of solid tinned hook-up wire, small gauge such as #26.
Use tinned wire, as plain copper wire would be a distracting color. You may also find special-purpose "bus wire" but don't use a gauge that's too big as it will be hard to sew.
You'll need a power supply or batteries capable of delivering about 0.6-1 amp at 8-10 volts, but that design is not included in this Instructable. Instead, you might like this Super-Simple LED Driver Instructable. Or just use a 9V battery.
For testing the LEDs during construction, If you don't have a power supply, you'll also need one slightly-depleted 9V battery or one fresh 9V battery and a 330 Ohm resistor.
To finish the job, you'll need the following tools:
Solder and iron if you wish to solder (recommended but not necessary)
Needle-nosed pliers with wire cutter
Third hand jig (or make your own
Alligator-clip test leads