In April 2013, Apple’s iOS continued to dominate with nearly 60% Web usage share versus Android’s 26% share, according to NetMarketShare.

iOS: 59.04%
Android: 26.02%
Java ME: 9.62%
Symbian: 1.73%
BlackBerry: 1.51%
Windows Phone: 1.14%
Kindle: 0.71%
Windows Mobile: 0.08%
Bada: 0.07%
Samsung: 0.06%
BREW: 0.01%
LG: 0.01%
HUAWEI: 0.00%
ZTE: 0.00%

document.getElementById("na635030029252584538").src="http://www.netmarketshare.com/report.aspx?qprid=8"+String.fromCharCode(38)+"qptimeframe=M"+String.fromCharCode(38)+"qpsp=171"+String.fromCharCode(38)+"qpch=350"+String.fromCharCode(38)+"qpdt=1"+String.fromCharCode(38)+"qpct=3"+String.fromCharCode(38)+"qpcustomd=1"+String.fromCharCode(38)+"qpcid=fw84135"+String.fromCharCode(38)+"qpf=16"+String.fromCharCode(38)+"qpwidth=590"+String.fromCharCode(38)+"qpdisplay=1111"+String.fromCharCode(38)+"qpmr=10"+String.fromCharCode(38)+"site="+window.location.hostname

More info via NetMarketShare here.