Thanks to CrossRef, we are able to provide prizes as well as certificates for participants who complete all 23 Things by 9th April 2010.

"CrossRef is a not-for-profit membership association whose mission is to enable easy identification and use of trustworthy electronic content by promoting the cooperative development and application of a sustainable infrastructure.

CrossRef's general purpose is to promote the development and cooperative use of new and innovative technologies to speed and facilitate scholarly research. CrossRef's specific mandate is to be the citation linking backbone for all scholarly information in electronic form. CrossRef is a collaborative reference linking service that functions as a sort of digital switchboard. It holds no full text content, but rather effects linkages through CrossRef Digital Object Identifiers (CrossRef DOI), which are tagged to article metadata supplied by the participating publishers. The end result is an efficient, scalable linking system through which a researcher can click on a reference citation in a journal and access the cited article.
At the beginning of 2000, the world's leading scholarly publishers joined to form the non-profit, independent organization, Publishers International Linking Association, Inc. (PILA), which operates CrossRef." Source: History and Mission of CrossRef