This shipped after SQL Server Reporting Services 2008 and is available as a separate download. I have always run a search to download the latest installation file.
Report Builder 2.0 is a too design to allow the easy and quick development of Reporting Services Reports and was created with the non-developer in mind. This is reflected by the fact that it looks like MS Office.
It can be started by selecting Start > All Programs > SQL Server 2008 Report Builder > Report Builder 2.0.
Once you have opened Report Builder 2.0 you will notice there are 4 tabs Run,Home, Insert and View.
The Home tab contains Clipboard, Font Paragraph, Border, Number and Layout.
Insert tab has Data regions, Report Items, Sub reports, Header & Footer.
View tab has Show and Hide.
The Run tab has Views, Zooms, Navigation, Print, Export, Options and Find.