Three Internet companies—Nextag Inc., Yelp Inc. and Expedia Inc.—are gearing up to attack Google Inc. on Capitol Hill, claiming the company is taking new profits for itself by unfairly punishing them on its search engine.

In a preview of Wednesday's Senate antitrust hearing on whether Google abuses its dominance on the Web, representatives of the sites—which help people search for information on consumer goods, local businesses and airline flights—said in interviews this week...