Vector programs make life much easier for us. We have more control over the specific colors in the design and we can resize to our heart’s content. Personally, I use Illustrator, but Inkscape‘s a decent, free alternative. And it’s now been joined by Aviary’s Raven, which has just been released.
It has collaboration tools, and it’s online, so there’s no installation necessary. I need to spend some time playing with it, but it looks pretty cool.