I've got a HD project in CS4 and I want to deliver a SD file or files that can be imported into Pinnacle or FCP so another editor can work on my footage. I've used a couple of plugins that they wont have so I need to export to something? - but what?

Use a generic mpeg2 preset within media encoder; whatever preset works best for the sd file type you want to give them (i.e., framerate, size, aspect ratio, etc.)

great - thanks for that

Exporting mpeg2 will be lossy. If filesize isn't a constraint, considering exporting to avi using a 'lossless' codec like huffyuv or lagarith. You and your collaborator will both need to install the same codec, but they are small downloads and free.