The Better Business Bureau (BBB) - There are more than 2.5 million organizations listed on the Better Business Bureau. Check if the company is listed in the local chapter of  the BBB and its rating. Newer companies may not be listed. You can also register your complaint if you feel you have been treated unfairly.  There are local bureau in various cities and towns in USA. However BBB is only a non profit organization, registration is not compulsory
 

The Federal Trade Commission's Consumer Response Center 

Read their report on theenvelope stuffing scam . No  company can afford to pay US$1-5 for simply stuffing envelopes. You will be asked to pay an upfront fee (usually more than US$20)  and receive a starter package. However, the starter package will only contain instructions on advertising the envelope stuffing business. Participants in this scam are now legally prosecuted and fined if found guilty.

For craft assembly, you pay an upfront fee to purchase a kit . You are promised a very attractive fee for the product which you can assemble from home in your free time. Usually the assembled product,  rarely meets the stringent "quality standards" of the kit supplier and the kit buyer loses money.

Scambusters -  http://www.scambusters.com/
The National Fraud Information Centerhttp://www.fraud.org/

How to check online if a company is a scam from the company's website