I don't really make skins, I just edit them to my liking. I could most definitely make skins, I just choose not to because I don't have the time. Anyway, me bragging aside, I use paint.net (not a website, it's an application) to edit my skins. On the other hand, to create skins, I recommend using a website like minecraftskins.com. I used to make skins using their editor and it worked great!
