How to change my Minecraft skin without Minecraft.net?

I purchased an account from EBay, and the account I was sold required a security question to log into Minecraft.net. The seller had bought the account previously, and did not have the answer to the question. Are there any ways to change the skin of your Minecraft character while being able to play online?

Guest

Certain sites with skins can allow you to change it from the site. I think if you search a skin on planetminecraft it gives you the option to make it your skin.

Jake