For many new social networks, an invitation-only approach makes a lot of sense.

Not only can you focus on developing the community and its interactions, but when properly done you can also create a real demand for invitations.

Now, Dribble, a social network where designers, developers and other creatives can share samples of their current work, is leveraging that perceived value of an invitation to raise money for charity.

Dribble users are raffling off 25 invitations to Dribble to raise $5,000 for mycharity: water. That puts the value of a single invite at $200!

All for a good cause, while generating good will, media coverage, and even more interest in getting in the door.