I am pretty sure that there are a few apps on the net that automatically turns any picture into a cartoon look. There are plenty of camera apps on mobile phones that does just that. However, if you want to create the effect yourself by using photoshop, be prepared for a fairly laborious job. http://www.swftogif.com
It really depends on what kind of style you are going for. Everyone has already posted some very helpful tutorials. The big thing when doing Photoshop to remember is to simply experiment with it. I’ve fund that I learn the most with Photoshop simply through toggling with buttons and settings.