It's Opuntia microdasys, one of a group of tropical plants commonly referred to as Prickly Pear, though they rarely fruit if grown indoors. This particular one also has the common name 'Bunny Ears', well in the UK anyway.
General care instructions, if you haven't found them already, average warmth from spring to autumn, but keep cool in winter; 50-55 Deg F is ideal, but a temperature as low as 40 deg F occasionally will do no harm. Plenty of fresh air in summer or when temperatures are high enough, so near an open window if you're keeping it inside. Needs the sunniest spot available most of the year, but may need shading from very hot sun in summer. Water thoroughly when the surface of the compost is dry to the touch, but don't leave it standing in water in any outer tray or pot. In late summer, reduce watering a bit and after mid autumn, keep almost dry - just enough water to prevent shrivelling. Start watering normally again as spring arrives. These instructions apply to most desert type cacti, of which this plant is one.