Tracking Customer Contacts
Use the "Customer Contact" checkbox on every log entry that pertains to the contact with a customer. Each log entry (including status changes and milestone completions) have the option to explicitly indicate if the entry is related to a contact with the customer.
Here's an example of where user indicates contact with a customer:
In the project log, you can see the entries tagged with customer contact:
The Sales screen has a column showing the last customer contact:
Of course, you can also view the last completed milestones on the Sales and Installs screens too (which is also a log entry)
Use Project Detail Reports
SolarNexus provides a number of fields in Project Detail reports that give you details on tracking lead status and seeing latest log details.
Here is an example report showing current milestones with details (milestone, current status as of last change), last date log was updated, and date of last customer contact: