Most of the material that I have been able to find that discusses online faculty work and tenure has been related to the humanities. The Modern Language Association (2000) has posted these recommendations for faculty and committees making tenure decisions.
These general guidelines remind faculty to clarify their role at their institution, seek advice from administrators and senior faculty regarding types of work and to document their online work in a manner similar to other types of scholarly contributions.
The advice to committees reviewing promotion cases in regards to digital scholarship is to make sure that external evaluators are appropriate for this type of work, that the work is reviewed online rather than on paper (in order to fully understand the work) and to see advice from other disciplines that may be relevant to digital scholarship.
The MLA Committee on Information Technology has also established a wiki on the topic of digital scholarship that addresses a wide variety of issues and ideas about how faculty, administrators and faculty review committees can handle issues related to digital scholarship.
See all my delicious tags for p&t: http://delicious.com/hughesro/p%26T