XML

You can find some preliminary GPL'd DTDs at XML/DTD, the development of XML is moving to Sourceforge as soon as we can reach some decent project description for ConsuML (this is not a set-in-stone name, you can have your say at Polls).

Useful grammars in building Consumerium:

XML Based Signing http://www.w3.org/Signature/
XML Based Encryption http://www.w3.org/Encryption/2001/
XML Key Management http://www.w3.org/2001/XKMS/ (Working Group)
XACML (eXtendable Access Control Mark-up Language) from http://www.oasis-open.org/
GML (Geography Markup Language) from http://opengis.net/gml/01-029/GML2.html
SVG (Scalable Vector Graphics)

XML tools

Largest collection of Free XML Tools on the web

Grammars that should be made interoperable by XSLT transformations in ConsuML

Market Data Definition Language (MDDL) is used to describe financial market phenomena and interchange data between market participants. This seems to be it's way to becoming an industry standard. It uses the following standards in it's markup.
Electronic Business XML - Developed by OASIS and endorsed by UN
IXRetail - US retailer federations proposal for XML for Retail functions
- ISO 639 - Language Codes (2 char), ISO 3166 - Country Codes,
- ISO 4217 - Currency Codes (3 char,)
- ISO 6166 - International Securities Identification Number (ISIN)
- ISO 10383 - Market Identification Code (MIC)
- ISO 10962 Classification of Financial Instruments (CFI)

EAN.UCC Global Data Dictionary is an attempt to standardise XML business messages. This initiative doesn't seem very active lately

XML data sources

GEPIR @ http://www.gepir.org (Gateway to searching EAN, SSCC, GLN)

Otherwise Interesting

RSS for your information overdosage needs.
OPML for exchanging collections of RSS feeds

External links:

http://www.w3.org/