The code is pretty simple, but it's nice to have this snippet around when you need it.
Dim ReportURL as string = "http://www.figers.com"
Dim js As String = "<script language=""javascript"" type=""text/javascript"">
window.open('" & ReportURL & "');</script>"
Page.ClientScript.RegisterClientScriptBlock(Me.GetType, "NewWindow", js)