THe 24" Cinema uses MiniDisplay. SO you'll need Belkin's HDMI to MiniDisplay to start. Does the Pi use a digital or analog video out? Fingers crossed it's digital, probably Dvi, so you'll need a cheap DVI to HDMI. So full adapters will be Pi port to full length Dvi, DVI to HDMI, then Belkin converter to MiniDisplay port. If the Pi outputs directly to HDMI, then just grab the Belkin adapter.