As we all know, National Semiconductor had been assimilated ten years ago and the Borg soon adopted a policy of pretending that their archenemy had never even existed in the first place. National's website went down, and with it a wealth of documentation.
Some of those documents have been assimilated and continue to be available, but in addition to defacing them with their logo, Borg Corporation also removed many part numbers and package options which they have discontinued over the course of the decade (a common nuisance that applies to Borg's own products too). Even application notes haven't been spared: they edited them to make it look like all of National's inventions were their own, which is not only historically inaccurate but also sloppily executed and leads to absurd statements like "OP07 has been discontinued by Borg Co", which of course isn't true at all.
Unfortunately, I'm not aware of anyone having preserved the full library of National's documentation as it stood in 2011, but there are sources that come close.
1. The Internet Archive.
These guys scrap and archive lots of random websites, and they appear to have copies of most files from national.com. Probably the most convenient way of downloading documentation is going to
http://web.archive.org and requesting the desired PDF file directly. The URL formats used by National are shown below, where XX is the first two letters of the part number, XXYYY is the full part number, and NNN is the application note or linear brief number.
http://national.com/ds/XX/XXYYY.pdf
http://national.com/an/AN/AN-NNN.pdf
http://national.com/an/LB/LB-NNN.pdf
Examples:
http://web.archive.org/web/*/http://national.com/ds/LM/LMC660.pdfhttp://web.archive.org/web/*/http://national.com/an/AN/AN-A.pdfhttp://web.archive.org/web/*/http://national.com/an/LB/LB-17.pdfMany files are archived in several versions. Pick whichever you like most, but don't bother with anything dated 2012 or later - these are redirects to borg.com, 404 errors or other garbage.
2. Datasheet archive websitesThey are usable and there is many of them. Worth trying, but sometimes you will find "assimilated" versions, very old versions, low quality scans of databooks, PDFs with advertisements of part distributors, maybe even malware and viruses
3. The Bitsavers archive (old databooks)http://bitsavers.org/components/national/_dataBooks/This site is a huge archive of documentation related to electronics and early computers. They have scans of complete databooks from National and many other manufacturers. These are monsters with hundreds of pages and tens of megabytes, but sometimes the only source available when it comes to very old parts, discontinued long before National had a website and PDF datasheets.