I have a CRM template on my site, it might be close to what you want. I
based it loosely off
the Microsoft CRM web package. It has Accounts, Contacts, Opportunities,
Activities (Tasks, Phone Calls, Faxes, Email, Letters, Appointments, Service
Activities) and Invoices.
Also security and some other nice features.
Depending on your definition of "lead":
Accounts/Contacts with a status of Suspect haven't bought anything
Accounts/Contacts with a status of "Prospect" are involved in an opportunity
Opportunities are tied to an Account and possibly a Contact at that account
Activities are tied to Accounts, Contacts and/or Opportunities
http://navintmicrosoftcrm.blogspot.com/2007/09/what-is-lead-in-microsoft-dynamics-crm.html
You can download a free eval and try it out,
It has a lot more substance (and code behind it) than the typical free
template and it's cheap,
At a minimum it's probably a good starting point,
HTH,
Mark Andrews
RPT Software
http://www.rptsoftware.com