>>329
COMのMicrosoft Internet ControlsとMicrosoft HTML Object Libraryを参照

using SHDocVw;
using mshtml;

ShellWindows sw = new ShellWindows();
foreach (InternetExplorer ie in sw)
{
　　if (System.IO.Path.GetFileName(ie.FullName) == "IEXPLORE.EXE")
　　{
　　　　IHTMLDocument2 htmlDoc = (IHTMLDocument2)ie.Document;
　　　　Console.WriteLine(htmlDoc.url);
　　}
}