The solution pointed to by Piet is a good starting point. I'd modify it to do something more along these lines:

SELECT

Catalog.Type,

Catalog.Name,

Catalog.Path,

MAX(ExecutionLog.TimeStart) AS lastUsed

FROM

dbo.Catalog

LEFT JOIN dbo.ExecutionLog

ON Catalog.ItemID = ExecutionLog.ReportID

WHERE

Catalog.Type = 2

GROUP BY

Catalog.Type,

Catalog.Name,

Catalog.Path

The LEFT JOIN ensures that you will get all the reports currently with a NULL in the lastUsed column if there is no longer a row in the Execution Log because the last use has aged out of the execution log.