You can report it to http://www.ic3.gov/complaint/default.aspx but they won't act on any one complaint.
Sending fake checks through the mail is a crime so contact the US Postal Service Inspectors https://postalinspectors.uspis.gov/forms/MailFraudComplaint.aspx
It's difficult to stop scams like these in real time. The only thing we can do is to warn others and to try to cripple his scam operation as follows. If you received an email and can read headers or know someone who can, you can report abuse to the sending email service and have his account terminated. Ditto for his reply email address if different from his sending address. This will only slow him down, it will not stop him.
hello everyone...i haave this dude on the hook to should be reciving the first check on monday......let me know what i can do to help catch this dude ...i was recently burned by another person....luckly i was smart enough to have my bank check the money orders but they still threw me out of there bank i will never be allowed to bank there again that sucks.....lets get these but munchers