Step One

OK, choose you’re image - I’m going to use the lovely sunset shown - try a person for a very nice effect (see step 3).
Step Two

OK, with you’re picture open, go filter–artistic–cutout and use the following settings (or tweak them depending on what you’re looking for!)
Cutout
Number of levels: 8
Edge Simplicity: 3
Edge Fidelity: 3
And thats it! Press OK and you have a vector-looking image.
Conclusion

Well that was the simplest tutorial I’ve ever written, but I got a request and when I reslised how easy it was to ‘fake’ vector I thought I might as well show everyone else - remember this isnt *really* vector at all, but its a nice technique if you’re tight on time and need it!
I’ve also shown how this looks when used on an image of a person.