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.
The 754 (2008) draft you link to is reasonably close to the final standard in content, but there are definitely a number of significant changes that came in the two years between that draft and final publication (I'm "STC" from the change history, for context).
It's not hard to find copies of the final standard online, but the availability issue is definitely something that the committee is aware of.
I don't know, that seems bad just in a different way. Maybe if IEEE hosted those documents themselves it would make sense to link to them but even then the copyright notice on the draft looks pretty onerous.
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.