Anyhows, with regards to how signatures are made, you create them using an image editor. There are probably some websites out there that could make them, but I doubt it.
If you wish to help other members out by making them signatures, you will definitely need to know how to use some form of image editor, with Paint being the absolute minimum. You'd want Photoshop, GIMP, Paint.Net or Fireworks for advanced image editing amd manipulation.
Also, moving this topic to a more appropriate location.
I'd recommend using GIMP or Paint.NET, since they're both free but are still pretty beefy programs. Then it's just a matter of figuring out how to use the programs to manipulate pictures to your liking, as well as adding other pictures or adding text. I made my signature with Paint.NET.