I've had tinnitus in my left ear for about 7 years. It's a continuous monotone hissing like the sound of a tire forever deflating. That was accompanied by a moderate loss of hearing in that ear.
The tinnitus in my right ear is much more amusing because it changes periodically. It started mid December of 2011 at about the same time I discovered that I had almost completely lost my hearing in the right ear.
In December, believe it or not, it sounded like wind chimes playing Silent Night. Appropriate, I guess, for the Christmas season, but just as annoying as the relentless Christmas music from other sources.
Over the last 6 months (in order of appearance) it changed to a sound similar to the repeating tone of a tuning fork, then to a sucking noise, and currently sounds like the intermittent boop, boop of Morse Code.
Fortunately, the volume of my tinnitus has always been rather low and barely perceptable so it's been fairly easy to adapt to and ignore, especially when my attention is on other things and there are other sounds going on.