Make Transparent Images

I was trying to figure out a quick way to make an image transparent for a Keynote presentation. What I landed on was a tool I've used quite often in my Tech Class called LunaPic. LunaPic is a superb tool for doing cool stuff to images, sorta like BeFunky, but it seems to work better on some of our school machines (flash issue?).

It's very easy. Upload your image, go to Edit > Transparency, and click on the color you don't want (in my case the background). LunaPic will get rid of that color and you're left with a transparent image. When you save it I found it's best to save it as a GIF. JPG just gave me a black background.