A ballast is kinda like a preamp in music, or a powersupply for a computer. Basically it regulated the power into the bulb.

HID lights are a little heavy-duty for a countertop. AHL is a good supplier of HID lights. The lower-wattage options might be good if you can hang the light above your countertop. (The ballast, which is heavy, can sit on the floor.)

Otherwise, check out Indoor Gardening Supplies, another excellent supplier that sells plant stands, including carts and some self-contained desktop models.

Here's a photo from an indoor garden I grew under an HID light.