I read some responces and it looks like a ton of people already suggested fleas -which was my first reaction too. And like soekone already said, even if you don't have a pet there could still be fleas.
I have a couple suggestions for bug though - someone mentioned salt on teh floors, but what will work even better is borax - it is sold in teh laundry detergent asle as a laundry aid. Its cheap- about $4-5 a box - srpinkle it around the preminter of your home (if its a condo call the association's exterminator for outside spraying whch is usually always included in the fees adn will cost you nothing) and then take the borax and sprinkle it into teh floors, let it sit a few hours and then vaccum it up.
When I moved into my new house the previous owners had a dog that had fleas- BAD fleas and so I did the borax thing on teh outside and in the floors inside throught the house. I also have a chihuahua- poor guy got attacked but he only had to suffer for about a day or 2 until his FRONTLINE treatment kicked in and killed all the fleas in the house.
Maybe it was the borax, maybe it was the FRONTLINE, maybe it was both?
If you have a pet - bite the bullet and spend the $60 on teh FRONTLINE, if you don't try borax.
Also- if could be flies - there are some flies that bite too and their litlte red bumps look like flea bites but bigger although not as large as misquito bites.
Good luck!
@}~>~~