Women traveling alone in Europe likely will get stared at, groped and talked to by foreign men. But guess what? So will women traveling with others. I know this from nutty, annoying experience. So don't let that be the thing that prevents you, if you're female, from traveling solo.
At reidsguides.com there's a funny post called "Ciao, Bella, Americana Girl," where Reid explains what to expect from "Italian Romeo wannabes to overly gallant Frenchmen to icky Greek shopkeeps." Was he with me in Europe when I was in my 20's and 30's? Because, check, check and check on those Italians, Frenchmen and Greeks.
In Italy I traveled with my friend Adele. In France I was on my own. In Greece I was with a boyfriend. And in each place, I ran into men behaving badly.