dust bunny

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A mass of fine, dry particles of matter, especially hair and skin particles, that is formed by static electricity.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic A small clump of dust, fluff, hair, particles of skin, etc. that tends to accumulate indoors in areas that are not regularly dusted, such as under heavy furniture.