Granted, this is just anecdotal, but almost every "socially conscious" Jew I know (who has a facebook account) has added the application for "causes."
For instance, Dan Sieradski (one of the most socially conscious Jews that I can think of) has four: Jewish Funds for Justice, Jewish Council for Public Affairs, End the British Boycott of Israeli Academics, and Brit Tzedek v'Shalom. For the record, the available causes are not exclusively Jewish; IRC is represented, so is Save Darfur, and the list goes on.
According to the facebook "about" page "Donations to causes can benefit over a million registered 501(c)(3) nonprofits." The way it works is that a facebook member puts a/several causes on their profile page. They then recruit others to do the same, and also to donate money. Money is donated via credit card (you get an electronic receipt). 95% goes to the non-profit, 3.5% to the credit card company, and 1.5% to Project Agape, which provides support for the application. (More information at MYDD)
Allan Benamer of Non-Profit Tech Blog points out that being a part of facebook, in whatever capacity, is a huge business advantage. In this specific capacity, as the facilitator of "causes" they have the ability to leverage the entire charitable giving of the facebook membership through the site. There is currently no other non-profit alternative. Ahhri of Ari Says points out that this facebook application is the "ultimate in positive peer pressure."
And here is where my pessimistic critique comes in. At first I saw the causes application and was really excited by the possibilities. Non-profits can raise money directly from young people, get out their message, and create a coalition, all with very little/no overhead. They can take the raw numbers of people who have added the cause, and be able to say that the represent a certain constituency. Unfortunately what I've seen is that the causes, by and large, have just become an extension of the "groups" function. A statement of belief, with very little action.
For instance, the Human Rights Campaign has over 12,000 members, yet only $712 has been donated to date. From what I can see (I haven't added any applications, I don't want their creators to have access to my personal information) the numbers are the same across the causes. Many people join, some recruit friends, very few actually donate/raise any money.
It seems again that my generation has proved to be (so far) all talk and no action. Even when we bring the mountain very close, we can't manage to take (much) action.