Tried lots of different brands and styles. I used to use the foam roll-up earplugs, and they were good.
I've had 2 pairs of "custom-molded" plugs made with mediocre results.
A few years back, the Iron Butt crowd introduced me to Etymotics, designed for musicians and sound engineer-types, and they are extremely comfortable with their 3-flange silicon construction. They are comparable or superior to the Shure e-215s mentioned here earlier.
The model numbers change over the years; I've had one pair of Etymotics ER6 for at least 5 years before one channel went out - I probably yanked it or crimped it. I bought a less-expensive model, around 80 bucks or so on Amazon.
I listen to music or podcasts while riding, so wind noise elimination and sound quality are of primary importance to me... after extended wear comfort, of course.
EDIT: They wear well under a helmet, don't interfere with wearing or un-wearing my Shoei, and a helmet liner makes it even easier. Easy on, easy off. Don't forget to release your helmet retention system first.