In the last quarter three charity/social networking mashups have crossed my desk, each with their own distinctive tang. All three are in beta, that is, they’re works in progress. All are for-profit endeavors. All could benefit from a little ‘network effect’ love.

The network effect aka Metcalf’s Law postulates that the value of a network is proportionate to the square of the number of users. That is, a network only starts demonstrating value after reaching the critical mass described by the equation.

In other words, each of these outfits has some selling to do.

uPlej. With an approach that could probably only come from Utah is uPlej, which owes its business model as much to multi-level marketing as it does to Facebook.

Here’s how it works: you sign up as a member of uPlej and designate a charity, create your own profile, alert your personal network to your new uPlej page and UPlej dings your credit card for $4.99 a month. Of that, $4 goes directly to the charity, and the remaining $0.99 goes to uPlej’s operations and fees for processing credit cards and the like.

What’s the appeal? Well if just 4 of your friends also join uPlej, then your designated charity could receive perhaps $85 a month (more or less)! Here’s how: “The charity calculator works on the premise that each of your ‘friends’ tells just 4 people each, who tell just 4 people, and so on through 3 degrees.

“For every person you tell that visits your user page and signs up, you receive $1.00 for the cause YOU have elected to support. For every person they tell that visits their user page and signs up, you also get $1.00 for your cause, and so on through 3 degrees. Everybody that you tell that joins your network is your first degree, everybody that joins the network of anybody on your first degree (anybody that they tell), becomes your second degree, and so on. This gives you the opportunity, for only your $4.99 monthly payment, to raise a significant amount of money for your cause every month—simply by connecting with other charitable individuals.”

As I write this, you can choose from uPlej’s universe of 150 charities, a number they’re working hard to increase. uPlej is not a charity, it’s a fundraising company that uses the power of a networked downline to raise money for charities.

Just Cause. Like uPlej, Just Cause is a for-profit entity as well. But they prefer to think of themselves as a ‘for-benefit’ company, ala Newman’s Own and Peacekeeper Cause-Metics. Just Cause bills itself as “social networking with a purpose.”

Causes, individuals, and companies can all set up accounts and start talking about what their doing to make the world better, mainly through blogs. You can create or join user groups, post events, seek volunteers, donors, supporters, etc.

There’s more than 150 blogs currently being posted on the Just Cause site and about 60 nonprofits. Just Cause also publishes a magazine by the same name, expects to sponsor community events. The magazine is distributed with participating ‘city magazines’ in Seattle, Atlanta, Chicago and elsewhere. Just Cause says that the glue that holds all the pieces together is its approach to telling ‘stories.’

Do Good Channel from good2gether. The Do Good Channel is a kind of localized charity directory that allows you to search charities by type, participation, opportunities. But what really sets it apart is that it can also generates income for participating charities and enables searches that connect current news with charitable missions.

Here’s how. good2gether gives an Internet ‘widget’ to local TV, radio and newspaper media outlets. When a story is posted about, say, the crisis in Darfur, the widget points to local nonprofit resources that are working on the problem. The widget displays information in a frame on the media outlet’s website, which it can sell. If the reader clicks on one of the nonprofit links, it connects to a Do Good page where they find a profile of the pertinent nonprofit(s).

The profile or elements of the profile can be emailed, sent to Facebook, added to your calendar, etc. The profile is free to the nonprofit and relatively easy to generate. Better, the charity can sell the sponsorship of the page which it splits 65:35 with good2gether, which operates Do Good. To participate in this part of the service, the charity has to agree to charge a minimum of $100 per sponsor and limit it to no more six sponsors.

good2gether launched the Do Good Channel in Boston this month and is scheduled to add several top 10 markets per month over the next few months, including San Francisco, New York, Chicago, Houston, Los Angeles, Philadelphia, and Washington D.C.

There are elements of cause-related marketing in each of these approaches. uPlej enables a kind cause-related marketing for your personal brand, (although there’s no reason why a company couldn’t be a uPlej member too). Just Cause could certainly host a blog about your cause-related marketing campaign. The Do Good Channel in effect invites charities to connect to sponsors.