var selectmenu=document.getElementById("products")
selectmenu.onchange=function(){ //run some code when "onchange" event fires
var chosenoption=this.options[this.selectedIndex] //this refers to "selectmenu"
if (chosenoption.value!="nothing"){
location.replace(chosenoption.value, "", "") //open target site (based on option's value attr) in new window
}
}