These things are great! Splice wires together for strong electrical connections without using a soldering iron. They’ve got hot-melt glue in both ends and a melty bit of solder in the middle. This makes a waterproof connection that’s stronger than just using a soldering iron and heat shrink tubing.
I found them on Amazon, and they will soon be carried by Adafruit.com. They come in a variety of sizes. For 26awg wire, which I use in most of my electronics projects, the red-striped ones are just the right size.
I really love these things, especially for larger installations or projects where I can’t easily do repairs or hookups on my soldering table.
Animated gif by meee! Get yourself some, you won’t be sorry!