There are legitimate ones out there, believe it or not.
An article from the New York Post highlights one:
NO (WORK) PLACE LIKE HOME By TORY JOHNSON - Jobs - New York Post Online Edition - New York Post
There's even a forum (mostly for stay at home moms it appears, but the information still seems to be good) dedicated to companies that hire people to work from their homes.
Work Place Like Home - Powered by vBulletin
One of today's biggest growing small business is
ChaCha. Ask Away., a sort of human powered search engine for people to ask questions by text message from their cell phones. The founder of this company is the guy who pioneered voicemail technology. They pay people to answer questions from home.
Some of these pay by volume, some by the hour, but for people who for whatever reason find that conventional work may not work for them, this kind of thing may be a great alternative. Since you can knock out commuting costs, wear & tear on vehicles, uniforms, time wasted, etc. some of these look competitive.