I'm currently saving up to upgrade my kit lens. I do have a 70-300mm that I use to shoot birds and animals, but unless I'm specifically shooting birds and animals, I pretty much keep the 18-55 kit lens on the camera.
Here are a couple resources I've found while trying to make my decision on what lens to buy next:
Video from CameraLabs.com on upgrading the Canon kit lens:
http://www.youtube.com/watch?v=vm3f7eF4W3g
SLRGear's article - "Your Second Lens"
http://www.slrgear.com/articles/secondlens.html