I just use a drop-in infuser in a mug, especially when I'm trying a variety of different teas -- I don't want more than one cup in those cases. I use the SwissGold one, the 200, not the 300.
And an electric kettle to boil the water.
And if more than one cup, then a larger infuser and a teapot.
I tried the ingenuiTea from Adagio Teas (which is a similar item to the above), but I didn't like the way the lid wouldn't come off to throw it in the dishwasher (supposedly it does, but I couldn't figure it out without worrying about breaking it).