Nabbr, a Chicago firm that specializes in digital marketing and widget development, brought in $2.57 million in a second round of funding from Allen & Co., Avalon Ventures and undisclosed others. The company has typically focused on widgets that market music on social networks but says it would like to diversify into other types of entertainment going forward. It has already produced apps used to advertise the films Iron Man and Mamma Mia. In the past, it has raised money from record label S-Curve and private individuals like Michael Wolfson, founder and chief executive of digital consultancy Rocket Fuel.