There are copies of The Feynman Lectures on Physics online at
They’re largish pdfs, so might take a while to download.
(I don’t know who I’m stealing from by posting these online, but if you enjoy them then you could probably do worse than making a small donation to Caltech.)
EDIT: Now free and legal to read online here.
Downloading now—thanks, this is exactly the sort of thing I was hoping for!