<p>I need to get the Folder size and display the info on a report (SSRS). I need to do this for a number of Databases (loop!). These DB's are websites' backends.</p>
<p>Are any samples available for this? Does xp_filesize and the like the right solution?</p>

Could you clarify who should do what in your scenario? Do you want SQL Server do get the info or do you want Reporting Server do that?
What exactly do you mean by "folder size"? Is "one folder, sum up each file" enough or does it need to be recursive? Either way, I'd go for a little custom .NET function that uses
```
System.IO.Directory
```
and it's relatives.