The transit of Venus is among the most rare of planetary alignments. Venus passes in front of the sun twice every century. Transits appear in close "pairs," so although you might have seen this special occurrence in 2004, it will not be visible again until December 2117.
Without optical magnification, Venus will appear as just a small dot against the sun. Using a pair of binoculars or a small telescope will provide a much more satisfying experience. But don't attempt to view the phenomenon, using any method, without special equipment. Looking at the sun for even a small amount of time can burn your retina.
On Tuesday, June 5, in most of California, you can watch the planet Venus slowly pass in front of the sun from 3:04 p.m. to 9:46 p.m. PDT.