WOK has released SimpArp, a free MIDI-Arpeggiator VST plug-in for Windows.
SimpArp features all the standard functions you might expect from an arp like host sync, shuffle, different play modes and so on.
SimpArp is the free version of WOK's upcoming D-ARP, a dual-arpeggiator plugin with some extras like interaction of the two units with scale chord generation.