The National Endowment for Science Technology and the Arts (NESTA) Futurelab produce periodic literature reviews on education and technology. One of the more recent reports looks at e-assessment. (A pdf version is available here.) It’s a little UK-centric, but a jolly good read all the same, especially as ‘open web’ examinations get an honourable mention. A short critique of the report is also available at elearning-reviews.org.