This may have already been mentioned before, but I have only just discovered that the East Sussex parish register images from The East Sussex Record Office have been scanned and are available to view via family search.

It didn't come up via the normal route of going to the map, clicking on England and then selecting England, Sussex, Parish Registers, 1538-1910.

I actually went in via the online catalogue to pull up the film number of one of the parishes with the intention of ordering the film via the local family history centre and in addition to the microfilm icon was a camera icon. Clicking on the camera icon took me to a log in screen and when I logged in I was taken to the actual images for that reel.

I don't know if all parishes have been scanned, but I would assume so, as they seem to originate from The Keep, East Sussex Record Office.