I used earbuds for many years prior to switching over to in-helmet speakers. What worked for me so that they didn't pop out was to loop the cord up and over the back of the ears and then plug them in. That way, when the helmet presses against your ears it holds the cord and prevents the earbuds from popping out if you accidentally tug at it or the wind catches the cord. My favorite earbuds were Ink'd Skullcandy which can still be found for 8 bucks at Ross. They sound better than any helmet speakers but obviously are not as simple to use as in-helmet speakers/bluetooth and after a few straight hours of riding they tend to hurt my ear canals.