I wanted to use a Multicast Transformation in SSIS 2005 but for some reason it never showed up. So I scoured the web for a suitable explanation. To my chagrin I couldn't find it.
Eventually, I figured out how to make the Multicast show up. Simply, right click on any transformation in the toolbox and click on Reset Toolbox. This will remove any filters applied on the Toolbox and show all out-of-the-box transformations.
Update: Another way is to click on Tools > Choose Toolbox Items and check the Data Flow/Control Flow component not showing up.