Did you catch my article on writing for encyclopedias and reference texts? (It was published while I was away).
And speaking of encyclopedias and reference texts...contributors are needed for a 2-volume project to be published by Facts on File, Day By Day: The 1920's. Read the full announcement here. Note: "We are assigning each contributor 1 year of daily entries for the 1920s. Each month of entries consists of approximately 7,500 words. From experience with this series, we estimate 1 month of entries requires approximately 30 hours of research and writing. The first deadline is March 7, 2007, for a minimum of 7 months of entries per contributor. The payment for each 12-month assignment is $2,500."