The Last Activity Date is a crucial information about an
Account/Contact/Opportunity or a Lead record in salesforce. The system defined "Last
Activity" field is not available on Page Layout, but available in Report, List
View, and API (including Formula Field, Workflow and Validation Rule) for
Account, Contact, Opportunity and Lead object.
In our different business scenarios, we prepare different reports
based on the Last Activity date field, to do some analysis on a list of
records.
Well, but what about if we are not looking at a list of records,
instead we want to analyze an individual record?
Solution is simple, we can create a custom formula filed to
auto populate the Last Activity date information, and populate the same custom
formula filed on the page layout.
I propose a graphical representation of the Last Activity date information as below:

I hope you all find it interesting as it looks to me!
Following are the steps to achieve the above output:
1. Create a new custom formula field with “Text” formula
return type.
2. Put the following code into the formula syntax:
2. Put the following code into the formula syntax:
image("http://chart.apis.google.com/chart?cht=gom&chd=t:&chs=200x75&chco=00FF00,FFFF00,FF8040,FF0000&chxt=x,y&chxl=0:||1:|Recent|Old&chd=t:"&TEXT(Today() - LastActivityDate)&"&chl="& TEXT(Today() - LastActivityDate)&"+Days+Ago","Last Activity")
3. Finally include the same custom formula field on the page layouts.
Thanks.