According to XiTi Monitor, Internet Explorer's share of the browser market has dropped to 66.1% and Firefox has risen to 28%. Opera and Safari trail behind with 3.3% and 2% respectively. Firefox seems to be catching on faster in Europe than the U.S. and Asia.
However one has to be a little skeptical of these numbers since XiTi doesn't seem to provide any indication of the uncertainty in their figures. It's hard to believe they can really be accurate to ±0.1% in all these different countries.