Firstly, can you provide more information?
E.g. How long is the timeout, what is the query (provide SQL), how many rows, an example of the data and the purpose of the report - why is the data so huge?
Does your report really require huge data?
I have had situations where detailed reports are required for legally defensible reasons, but that is extremely rare. If you must have a lot of data on the report, you will have to break the report up into chapters and run them separately. You will find that this is not a reporting services issue per se, for example you will run into similar limitations with crystal reports.
One common issue that people have with reporting services is that they try to bring a huge dataset into the report and then use filters within the report. That is the wrong way to do it, you are better to filter the data in the SQL. Let the SQL engine do the work to optimise and minimise the required dataset.