ConcreteFX have released Ensembler, a free Arp type string synth VSTi for Windows.

Ensembler is mainly for produce string / pad sounds but can also do leads and basses You can find out more and download it from this thread in the forum.

Features:

• 6 osc using either saw, square, exp or triangle wave. You can control the coarse tuning of each of these osc's between -36 semi to +36 semi.
• Unison - this controls the fine detuning between the osc's and how this detuning changes overtime.
• ADSR envelope.
• Vibrato / Tremolo / Modulating Stereo widening.
• 10 type filter (12/24db low/high/bp/br + ring/comb) with att/rel envelope and modulating LFO.
• 3 effects - tempo-synced delay, 4 part chorus / flanger and reverb.
• 16 presets and manual.