[dan_yall]

Free pdf is available here:

http://bayes.wustl.edu/etj/prob/book.pdf

It's always nice to see good things come out of Wash U. (Alum here.)

[Fixnum]

Unfortunately, it's only the first 95 pages.

[gwern]

There must be a fuller version floating around, though; my PDF version has 548 pages and ends with Appendix E, 'Multivariate Gaussian Integrals'.

EDIT: In case anyone wants to make me feel bad about pirating, Jaynes is dead, and besides that, I bought a hardcopy as backup.

[Wilduck]

I found the full text here:

http://www.naturalthinker.net/trl/texts/Science/Jaynes,%20E....

The first couple pages are a bit funny looking, but after that, there are all 500+ pages. It was the fourth result on Google for me.