Summary reports, which show a quick overview of account information, are available from the Summary tabs of:
A summary report is made up of two customizable areas:
Header content - summary information from the current entity. For example, click on the Summary Report button in the context of a case, and the header content is made up of case summary information.
List output - information from the entities linked to the current entity. For example, click on the Summary Report button in the context on a company, and the list output area contains information about related opportunities, cases, and communications.
A Summary report is unusual in that the Header information is defined in a Screen block and the List output is defined using reports.
Now the question "Can I create a new Summary Report?" could be answered easily with NO. This is because much of the summary report's behaviour is drawn from the dll. But the question can be broken down into a couple of other questions.
1) Can I add other list shown data from a new entity into a Summary Report? Could I include Project details in a a Company Summary Report?
2) Can I create a new simple report and have this run from a button on a new Entity's summary screen. Can I put a Summary Report button on the Project Summary screen?
The answer to both these is yes.
See the article "Custom Reports Settings and Summary Reports