Ok its not really Starcraft 3 but I do spend quite a bit of my time playing Starcraft FA5 which for some reason people are searching Starcraft 3 to find it . As the name suggests FA5 is a flash based tower defense game that only resembles Starcraft in the fact that it has the same race classes and basic game concept; it is not a remake of the original game in flash. In the game you play as the Zerg and build up your defense against a Terran and Protoss attack. Its not a new game but very few Starcraft fans actually know about it and it is a great game to waste time and get a little Starcraft play adrenalin going.
the game can be downloaded or played from newgrounds.com
Article from Gamersyndrome.com