acid.milch&honig has released acid rack 2.0, a completely reworked version of the small virtual analogue software synthesizer. It's available for Windows as a VST instrument plug-in. It's shareware but the free version is fully functional, albeit limited to 5 voices. The full commercial-use version costs $25.

Features:

• 5/10 voices polyphony.
• 2 oscillators with sync, FM and ring-modulation.
• 1 multi-mode filter (LP, HP, BP).
• 3 envelopes (2x ADSR, 1x AD).
• 2 LFOs (free/BPM-sync).
• 1 host-synchronized arpeggiator.
• 2 random generators (all parameters/osc only to boost creativity).