ON24, a provider of webcasting technology, has raised $8 million from U.S. Venture Partners, Canaan Partners, and Rho Ventures. The company has now raised over $46 million over an unspecified number of rounds. Previous raises were not announced. The company’s core technology revolves around webcasting for the enterprise, but it’s also recently gotten involved in virtual trade shows — think Second Life-like experiences, but specific to business interactions. Release.