Panasonic probably isn't one of the brands you associate with value electronics, but when it comes to headphones, the company has shown that it has several models that deliver excellent bang for the buck, including the Panasonic RP-HTX7 monitor headphones reviewed here.
These guys have been around for a few years (I'm sorry I didn't review them sooner) and can be had for anywhere from $30 to $50 online. They come in several different colors and are distinguished by what Panasonic calls "retro styling."
That styling may not appeal to some people, but I thought they looked pretty good and, more importantly, they fit comfortably, were relatively lightweight for over-the-ear headphones, and created a tight seal -- not only did they passively block out a lot of sound, but they didn't leak any sound, making them suitable for cubicle use at work.
True to their "monitor" roots, the RP-HTX7s have a single, fairly thick 3.9-foot cord and somewhat reinforced straight plug. The cord isn't as thick as the unwieldy one on the Audio-Technica ATH-M30, another excellent budget monitor headphone set. The Panasonic's cord is shorter and more suited to mobile use. However, it is worth noting that you will have trouble getting that beefier plug to fit in your headphone jack if you have a case on your phone.