To effectively track leads and opportunities one should consider a centralized web-based CRM solution such as Zoho or SalesForce.com for team collaboration, data preservation and relationship management. A static spreadsheet risks data loss if your computer crashes before hitting save and version control is a challenge. Since your contact data is constantly changing with tasks specific to each relationship and each lead's time frame, your method should include a task management system enabling notes and task scheduling for timely follow-up. Spreadsheets or websites lack these dynamic features.

HubSpot's new CRM is free & far less complicated than Salesforce. Might be a good fit for you: http://www.hubspot.com/products/crm