FXpansion has released Orca, a free experimental monosynth built to showcase some new technology that FXpansion has been developing. Based on detailed and accurate models of analogue synthesizer circuits and components, Orca excels at deep, squelchy basses and thick unison leads.
Orca is available as a VST instrument for Windows XP and Mac OS X Tiger (Universal Binary) and it is free, although you have to create a (free) user account at the new FXpansion website if you haven't already got one.