We are about to launch our crowd funding site. What is the most effective way to attract attention?

You have only one launch. It should not to be rushed. You are additionally launching within a newly created industry, which clearly will be watched by many. I would start by establishing your brand and value proposition. Do not spend much time on your differentiator as all competitors have not revealed themselves. Your brand differentiator is important, but Phase II.

I would launch with targeted press releases that discuss features and testimonials from the owners of the companies you seek to launch, i.e. why they went with your platform? If you conducted a beta test, include the results. Send the press release to local papers, national papers and trade groups associated with the industries of your offerings.

If you have not already done so, I would ask an Economics professor from a local university to develop a white paper on your platform, i.e. efficiency and fairness. When completed the white paper should be distributed to the same group where you placed the press release.

Good luck.