There's been a recent trend of museums having some of their paid staff contribute to Wikipedia articles relating to the museum's area of interest. Things like writing articles about paintings in the museum's collection, biographies of sculptors who the museum has a large collection of works from, etc. This promotes the museum indirectly (by getting their collection more exposure), but in a way that also aligns with Wikipedia's goals.

There's a fairly organized system to do outreach to such organizations and help them contribute in a positive way: http://en.wikipedia.org/wiki/Wikipedia:GLAM