If you're tempted to uninstall Visual Studio 2005 after installing Visual Studio 2008 (I've done that immediately), a word of caution... There is currently no support for SQL Server 2005 BI projects in Visual Studio 2008. This means that with uninstalling VS2005 you'll lose the ability to, for example, edit Reporting Services 2005 Reports. Support for RS Reports in VS2008 are planned with the SQL Server 2008 release (due next year), but currently there's no plan to support RS 2005 Reports, only 2008.
So... to continue working with SQL Server 2005 projects, you'll have to have Visual Studio 2005 installed, but... not necessarily the whole thing. If you already uninstalled VS2005, but need it just for SQL2005 BI projects, you can now install the VS2005 shell only. Bring out your SQL2005 installation, look for the file vs_install.msi and run it. After a minute or two of silence, the installer should report that installation was successful. SQL Server Business Intelligence Development Studio, together with VS BI templates, is now back [Without all the clutter that "regular" VS2005 installation brings along].
I can't figure out why Microsoft didn't include SQL2005 BI Projects support in VS2008. I mean - with VS2008 you get all these new and improved designers for wide range of technologies, but for BI projects you'll still have to use the old VS2005 shell. I Hope that changes soon.