I now have the translation which I commissioned of Eusebius De solemnitate paschalis, on the celebration of Easter. This will go up in HTML form soon, but I have moved PC and I need to do some setup before I can deal with the Greek text in the footnotes.
In the meantime I uploaded a searchable PDF of the text to Archive.org here. For some reason the uploader put my name as author — rather than Eusebius! — but I hope that glitch will be fixed by the time you see this.
UPDATE: The Eusebius is now online here. Many thanks to Andrew Eastbourne for translating it all for us.