The HubSpot free CRM is free and intuitive. They offer a startup program for discounted rates, if your needs marketing needs exceed their free tier.hubspot.com
Salesforce specializes in customer relationship management. It can easily scale to enterprise level, but is more expensive than other options.
Affinity is a relationship management platform that helps you leverage relationship intelligence to expand your network, support your portfolio, and increase proprietary deal flow.
User Interviews helps recruit users from their audience of over 200,000 vetted consumers and professionals to help you meet your user research goals. Or, bring your own audience and build a participant database for any type of research.