Interesting idea. You'd probably want something with a variable speed. Any coffee grinder's I've used in the past are pretty intense and I'd be afraid of having nothing but tobacco powder when you're done.
That said I could see the VitaMix blender working well for what you're wanting to accomplish but unless you have one or are getting one for the intention of preparing your food, it's a pretty hefty investment for cutting up tobacco
Pipedisciple: I tend to agree with Chris... a coffee grinder goes at high speed. I think it would turn tobacco to dust. There's this other thread on the forum about this "shredder" thing. Or you could try perhaps the infamous "SLAPCHOP (link here). Perhaps that would work ?
A coffee grinder would work fine. Just get a cheap one from walmart with a button and clear lid that allows you to control when the blades turn so you (not a programmed setting) have control over how coarse the cut will be. Just hold down the button for about one second, (maybe even half a second)then stop and look to see how the plug is looking, repeat until satisfied. You will not turn the plug into powder unless you go way overboard.
Yeah i used one when i broke my arm. as long as its not one with a time setting the ones from walmart are perfect. just dont hold the button down to long otherwise you will have dust instead of ground tobacco.
The best suggestion is the 'slapchop', or other hand operated choppers. Pampered Chef also makes a nice one. By using the hand chopper, as opposed to an electric one, you'll have better control over the tobacco and how coarse or fine you want it.
I've used a cheap one for years on tobaccos like Ten to Midnight, which are hard to break up. Mine is a cheapie with a "burst" button that allows you to go in half second bursts. You can get your tobacco any way you like it.
Smokey
I would suggest a metal grinder. The wood ones get sticky after a while and are hard to clean.
http://www.amazon.com/SPACE-CASE-Grinder-Magnetic-Medium/dp/B003U584OG/ref=pd_sbs_k_48
You can find cheap plastic ones at Indian grocery stores also but metal is the way to go.