http://minecraft.decx.org/ (http://minecraft.decx.org/)
Easy tool to use that allows you to make your own skins with the click of a...mouse.
another one that also works and that I've become quite fond of is
http://www.minersneedcoolshoes.com (http://www.minersneedcoolshoes.com)
it has the ability to upload things you have already created and alter them aswell as see what other people have made :)
the only downsides I've seen so far is their scripting is a little glitchy sometimes and the site is a little sluggish sometimes but other than that it works as intended as far as I've seen.