Another frequently asked questions in many SSRS forums is
How do I rename the sheets when exporting to excel?
When a report is exported to excel, the excel sheets are named based on the report name, which is not a user-friendly one.
Prior to SSRS 2008 R2, there is no way that these names can be controlled. But SSRS 2008 R2 has a new feature which allows the renaming of excel sheets.
Robert Bruckner gives a step by step account of how to achieve this. Have a look at his blog