Hello Robert.
There are several software packages that do this. I prefer Corel Trace, that packs with the Corel Graphics Suite.
Bear in mind that the results aren't as promising as you would think. I use it mostly to give images another 'feeling', just as much as an Photoshop filter.
Generally the results are good, but not indicated for 3D Modeling, because their aren't accurate.
Cheers
Quico
