Zoho, best known for Web apps like Zoho Writer and Zoho Sheet, offers just such a system: the aptly named Zoho CRM. It helps you with sales and marketing, inventory management, customer service, and more -- but it's not the easiest tool to learn, especially if you're new to CRM. Fortunately, Web Worker Daily shows you how to get started with Zoho CRM.
Step one, of course, is creating an account (if you don't already have one). Amazingly, Zoho CRM is free for up to three users, and that includes most of the features of the Professional and Enterprise Editions (which cost $12 and $25 per user per month, respectively).
From there you'll learn how to import business contacts, track and manage leads, manage customer support, and find Zoho's wiki-based help pages. It's definitely a handy walkthrough for anyone new to the system.
If you want to learn more, Zoho has a variety of demo videos that show Zoho CRM in action. For example, here's one that demonstrates how to designate a qualified lead:
Like this? Zoho offers lots of other goodies for small businesses, including Zoho Chat, Zoho Creator, Zoho Invoices, and Zoho People (which is not yet another social-networking site, but rather a human-resources tool).