In the UK there's "Ethical Consumer" which is a magazine and website. They cover a broad range of ethical issues people are interested in (for example, I might care that meat is free range, but not care at all if it's organic or not).
They recently had a petition that was partially responsible for getting Mars Chocolate to stop using artificial colorants. The organizers went this route instead of a boycott and is a good example of how the different tools can reach a similar goal.
I don't think you should let an organization do your own thinking. Sometimes when you dig a little you find that the situation is not black and white and that a boycott is not right or an ethical product is not that ethic after all.
I think the poster was asking more along the lines of "there is something I want to boycott, what tools are out there that can help me make it a movement" as opposed to just wanting to sign onto something another org was doing.
http://www.ethicalconsumer.org/