When confronted by closed standards with open drafts I generally just implement the last draft. I might buy the closed spec to check, but my code comments and documentation will all reference the draft since that is what people can read.

You might tuck a copy of these into your personal library in case IEEE purges them.

IEEE754 base document: http://www.validlab.com/754R/standards/754.pdf

IEEE754r draft: http://www.validlab.com/754R/drafts/archive/2006-10-04.pdf

Perhaps someone who has seen both versions can comment on how close these are to the closed versions.