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The Internet Engineering Task Force including its tao.
RFCs are readily available and are a key source of information. The authoritative source for RFCs is the rfc-editor. IETF drafts and descriptive abstracts are at IETF.
Thanks to some commercial sponsorship, the IEEE is making many of the IEEE 802 standards available for free download. The latest versions are still chargeable but after three months or so even those are made available.
ECMA remains a key source of standards, all made freely available, including a CD set of all ECMA standards and technical notes, released twice a year.