The sites below are great. The first is the home of blender, where you can actually get the program. Anyone interested in giving it a go, really should.
http://www.blender.org/
http://cgcookie.com/blender/
http://www.blenderguru.com/
http://blenderdiplom.com/
http://blendtuts.com/

Excellent Gary.. and you answered  my question about camera tracking maybe without knowing it. Yes blender now has the function. cool. Anyhow, you are on the ball thinking of combining 3d with puppets. One of my sons works at a 3D studio and the debate is still a time versus what you are trying to achieve thing, and what method is the quickest, cheapest and still achieves the results you want. Rendering in 3D is  still very time consuming, and for something super realistic it is  sometimes quicker to go shoot it live with a camera. But then if you are trying to achieve something not so realistic...
   Then there is the question of going so polished, you get away from the essence of what puppetry is...in some way. Now we have 3D puppets, and even 2D puppets now (which I use).I started experimenting with latex and realistic puppets a dozen years ago, but decided to stay with basic-geometric-simplistic, and stylized puppets (dare I say'muppet´style) for kid's sakes, but also adults who might like the style. I found the realism freaked or grossed out the kids, and even adults. However, now we are getting into  more movie type stuff, I am looking at the possibilities of going   more into the realistic creature realm again. The same goes for sets. How real do you go, and how can you maintain a style which people will like? I tend to go with a  little bit  realistic, but noticably not real. I am still thinking about the whole thing though
   Thanks for the links.

The motion tracking is pretty straight forward in Blender. There are some great videos on youtube of stuff people have done.
My plan for Blender is mainly for creating sets or backgrounds that would be too complex to do real time. Maybe like if I need a wide angle shot of a planet, kind of like they used to do on the original Star Trek, the matte paintings that would serve as background when they beam down to a planet. Also, any of the in space scenes with ships and such, really simple to do in Blender.

Im not a pen and pencil(or photoshop)artist at all, so using a 3D program gives me the ability to create scenes and other content I couldnt otherwise. Unless of course it's a stick figure project, then im the man.

I have a feeling anything I do will likely scream 'muppets'. Not because im trying for that, it's just what I grew up with and what im comfortable with.

   I get you Gary. I did a 'planet outerspace' thing earlier this year. I did a model for the spaceship, but  the planet side of things was sadly lacking.In another I did a plasticine moon which looks quite cool. In the future I want to do a longish  'at sea'  segment/scene and the water generation will fit the bill quite nicely there. I also use 3D skies, which are quicker and easier to manipulate than real ones,and  distant hills and mountains in the backdrops are faster in 3D than miniatures, and are pretty convincing. Midgrounds in miniatures is quicker, and real sets tend to be better for forground stuff. I got up to putting vegetation on the 3D hills and have not done any  more since then.
   I too am tending towards the  'muppet' look, as it is a style I like. It is a style which is at times simple and obviously puppet, can be sophisticated, but is not so sophisticated that it encroaches too much into 'reality'.Although it can exist in real settings, it is still obviously puppet... if you get my meaning. Yesterday, we did an improvisation with some letters and a couple lizards in a cave setting. I was saying to my wife that it would have fitted nicely in to Seasame street. I  might post one of them here if I get through today ok. I am hoping to do more of these sketches and hopefuly we can get them into someone else's kids programs.
   Are you going to post some of your  work? I'd like to see it.

Neat stuff! I have been wanting to experiment with 3D printing, but I haven't had a chance to yet.

Re: Blender, two more of the best sites to check out are the Blender Artist Forums (where many of the top Blender users hang out & share their work) and Blender Nation, which is the most popular Blender Blog.

I consider myself a live performer, yet  I have dabbled in making a few simple videos with my puppets.
Here's a web commercial I made last year for my neighborhood pizza shop:

hi guys , I managed to get through the day and uploaded one of the improv clips we did with the lizards and letters. This one is in spanish. A great for you to learn a little...

Well done  Terrence... how do you  spell NYPD?

Wow! How did I miss this thread.  I guess I've really been out of the loop, but yeah! this is my thing.  I've been setting up a film studio in a spare bedroom.  Since I am way off schedule I quickly began my shows second youtube season this weekend. First Patsy episode is about done. It is not easy. I'm attempting to show full bodies (have had to make some)I used my usual red curtain, but did a shot of Klooky in front of a peach/gold curtain in my bedroom and it looks great.  Backgrounds can make a big difference.  It is difficult to get interesting shots without me in the way but I'm learning.  Editing tools using cut aways is making things much more interesting.  Get ready to see Millie Haskins using a hula hoop.

Shawn just made this whole topic area recently. I love it also. Great to be on a website where the powers that be(Shawn)listen to us.