The style of "in-ear" phones that have rubber tips that create a seal, but don't insert deeply into the ear, tend to block out as much sound as a typical set of standard sealed headphones. I have an inexpensive pair of iHarmonix "in-ear ear buds" which sound...well, OK, and block out a good bit of noise but not in a "goodbye world" way. They're roughly equal to my Sennheiser HD280 full-size, sealed headphones in terms of blocking sound.
I like them for commuting via subway/train. As long as I'm not blasting my music (and I rarely do), I'm at least aware of announcements, etc., even if I have to stop the music to really listen.
My iHarmonix cheapies do their job and sound better than many cheapies, but Sennheiser, Denon, and others have similar designs that presumably are better quality.