No. There was, however, a planet recently discovered orbiting the star 51 Pegasi. For more on this planet see the questions in the section called Other Solar Systems.
About 6 months ago, there was a large comet called Comet Hally/Bopp discovered which is going to be quite spectacular when it starts to make its perihelion approach in 1998, but dozens of comets are discovered every year.
There was also a recent press report in Great Britain about a new planet discovered between the orbits of Mars and Jupiter, but this turned out to be a misunderstanding. Somehow, the word 'minor' had been dropped from the report of a new 'minor planet' discovery...or something like that. Believe me, if astronomers REALLY discovered a new planet it would be all over the news media and we would hear about it for weeks!