Envelope stuffing is definitely a scam. Most of those things are either a scam, or at least sound better than they really are. If you do a search for whatever topic plus the word "scam" (such as envelope stuffing scam) you will get a lot of results!
Apparently some of the survey sites are legit. There are surveys you can take that will pay you $5, etc. But the ones that pay the big bucks are usually where one person wins the money. So maybe 1000 people take the survey, and one person will win the $500 or whatever. Etc.
Transcription sounds like the way to go, or maybe building web sites or something if you know how. I think you can take one or two courses in medical terminology and then you could be a medical transcriptionist.