A number of major media companies have combined to invest a fresh $19 million in ad network and management tool Adify, reports ClickZ.

Adify's system allows a number of smaller, niche sites to band together in ad networks. The company serves up ads on the network owned by Washingtonpost.Newsweek Interactive. By taking a stake in Adify, major publishers could expand their ad inventory by identifying specific blogs or networks to join.

GE Media, NBC Universal, Communications and Entertainment (a unit of GE) and Time Warner Investments all contributed to that $19 million. GE and NBCU's stake was $3 million, part of a $250 million equity fund they've set up to invest in new media and tech ventures.