The latest news about close passes of asteroids and comets by the earth can often be found at the astronomy magazine online sites, and the NASA Solar System Exploration site, which are updated very frequently. These are often the best, most reliable, and easiest to access sources of information on fast-breaking, important, news stories in Astronomy. We can recommend:
Sky & Telescope Magazine - A popular astronomy magazine online site; current events in the sky, and news items about Astronomy.
Astronomy Magazine - Another popular astronomy magazine online site; current events in the sky, news items about Astronomy.
NASA/JPL Impact Risk Page - NASA/JPL Impact Risk Tabulation.