Looks like a specie of fungus gnats. They are harmless, but are a nuisance. The larvae (called maggots) feed on fungal growth - and fungal growth occurs just about anywhere in the home.

Places to check: 1) potted plants - particularly the drip-saucers (drain water, wash and dry, then water the house plants with a mild soapy water solution with a bit of indoor insecticide - conventional or organic); 2) the insides of bathroom drains in the sink and bathtub (flush with vinegar, then hot soapy water); 3) the condensation tray under the refrigerator and freezer (remove, clean and dry before replacing); 4) fungal and mold growth in showers, window-sills and other area where water or condensate may stand.