These are a variety of links I discovered while writing this book. They include communities of 3D printing enthusiasts and links to keep up with what's going on:
3Ders.org: 3D printer and 3D printing news available at http://www.3ders.org/index.html
Case Western: 3D printing design fails available at https://docs.google.com/document/d/142LhI2XYRTBgERyJMcjWn-MIb5Txo20lFNfDYIFxzbM/view?pli=1
Mashable: 3D printing available at http://mashable.com/category/3d-printing/
Oddee: 10 amazing 3D printed objects available at http://www.oddee.com/item_98686.aspx
Soliforum 3D printing community: http://www.soliforum.com/
Top 3D printing sites on the web: http://www.3ders.org/stats/20121209-top-100-websites-2012-in-3d-printing-industry.html
Blender Key Commands: http://waldobronchart.be/blenderkeyboard/
Using Blender on a Macbook: http://devnulldb.blogspot.com/2012/07/using-blender-on-macbook.html
The following are links to companies that create 3D printed objects from the models you submit:
Find a local 3D printer near you, the smaller services: http://www.makexyz.com/
Design Anything.com: Find custom figurines, awards, jewelry, and more available at http://www.designanything3d.com/
I.Materialize: Find objects up to 6 feet in size, 70 materials available at http://i.materialise.com/
Moddler.com: This is for industrial designers, fine artists, architects, and inventors available at http://www.moddler.com/
Ponoko: 3D printing and laser cutting available at http://www.ponoko.com/
Redeye: Service bureau for Stratasys available at http://www.redeyeondemand.com
Sculpteo: This accepts Blender files directly available at http://www.sculpteo.com/
Shapeways: To make, sell, and buy available at http://www.shapeways.com/
ZoomRP: Emphasis on rapid available at http://www.zoomrp.com/
The following is a list of 3D printers aimed at the 3D printing hobbyist. It's not intended to be inclusive because new 3D printers are springing up every day, but it includes the leaders as of now, and a few newcomers:
Airwolf: http://airwolf3d.com/
Bukobot: http://bukobot.com/
Cube: http://cubify.com/cube/
Felix Printers: http://shop.felixprinters.com/
Lulzbot: http://www.lulzbot.com/
Makerbot: http://www.makerbot.com/
Makergear: http://www.makergear.com/
Mbot: http://www.mbot3d.com/
Peachy Printer: http://www.peachyprinter.com/
Printrbot: http://printrbot.com/
Reprap: http://reprap.org/wiki/RepRap
Solidoodle: http://www.solidoodle.com/
Tinkerine Studio: http://www.tinkerines.com/
Trinity Labs: http://trinitylabs.com/
Type A Machines: http://www.typeamachines.com/
Ultimaker: https://www.ultimaker.com/
B9 Creator: Liquid resin available at http://b9creator.com/
Form Labs: Liquid resin available at http://formlabs.com/
The industrial 3D printers are the high precision, high quality, and high price printers. But you can find a service that uses them and have the service make your object:
3D Systems: http://www.3dsystems.com/
EnvisionTec: http://envisiontec.com/3d-printers/
Made in Space: http://www.madeinspace.us/
mCor Technologies: http://www.mcortechnologies.com/
Stratasys: http://www.stratasys.com/3d-printers
Surely you want to make your objects yourself but sometimes it's good to have a little help in modeling, especially if you are on a deadline. There is no guarantee that the models listed are 3D printer-ready though:
60 sites with free 3D models: http://www.blendernation.com/2009/03/23/60-sites-with-free-3d-models/
Blender Models.com: http://www.blender-models.com/
Blendswap.com: http://www.blendswap.com/
Next Wave Multimedia: Free Blender models available at http://nextwavemultimedia.com/html/3dblendermodel.html
TF3DM free Blender models: http://tf3dm.com/3d-models/blender
Thingiverse: http://www.thingiverse.com/