Best Cheap Design Package: Ailbre Design (as low as $50) http://www.alibre.com/ I used this before Solidworks, if the design isn’t extremely complicated this is the software to use. Make sure to find a coupon, they offer 50% off about every other month. There are 3 different price points depending on what you are doing. Very active community that helps newcomers learn.
Enclosure Prototyping in the US: http://www.protomold.com/ or http://www.quickparts.com/ I tend to use Quickparts more, but Protomold is also very good. All you do is upload the design and they price it. Also Quickparts offers samples that show you different finishes, materials, and designs problems to avoid. If new, definitely order one.
Design Guidelines: http://www.protomold.com/Resources.aspx Shows you the general rules on materials and design.
Outsourcing Design Work: http://elance.com/ or http://guru.com/ Excellent locations to find extra help, only accept companies after you have talked to them (I suggest IM for overseas) and only if they have sample projects and references within the US. Place a keyword at the end which they must reference in the bid so you know they read your requirements.
Electronics Prototyping in US: This really depends on the type of parts, the mount, and quantity. Generally though I use http://www.screamingcircuits.com/. For just a couple there are a few cheaper options.
Electronics Layout: http://www.cadsoftusa.com/index.htm It’s cheap and gets the job done for simple projects. They have a free version to test.
Parts Supplier: Small scale: http://digikey.com/ Large scale: http://arrownac.com/ If you get in touch with a sale or tech rep at Arrow they can be a great help in putting you in touch with oversea producers. Arrow’s website sucks so just find your local rep and call them.
Producing in China: There aren’t really any go to firms, it depends on what you are building. For rapid injection and electronic assembly I have used http://icomold.com, they even do design and prototyping. The design work is done in the US while the manufacturing is completed in China. They sell steel injection molds for the same price as a lower quality aluminum mold in the US.
The general rule when producing in China is to NEVER have a product completely assembled in 1 factory unless you want copies going out the back door.
How to do it: 1) Have the device produced in 1-2 locations without the software 2) Have the boxes produced 3) Ship the unboxed products to the US, (LA) 4) Hire a firm to box the product and flash the hardware
If there are more questions I would be happy to try and answer them.