Eoin's suggestion is a good one. If you make connection requests cold, be sure to include a detailed note, otherwise you'll be wasting your time. But as you said you're already using LinkedIn, I'm sure you know that.

IntroHive is good but it's really for enterprise customers who have an active CRM full of existing contacts.

A friend of mine has just launched http://www.thehonestcustomer.com It offers a unique approach to customer development in that it delivers surveys (pricing and customer development questions) to people who are your potential customers. You can define Industry, Company Size, and Job Title to target it very specifically. It's a good first step to creating the customer relationship.

If you want an eTro, just message me.