Cycling `74 has brought two of their popular Mac products to Windows users:

Pluggo
is a collection of over 100 effects and instruments developed in the
Max/MSP environment. It's an old favorite on the Mac, and Windows users
have waited a long five years for a native version. While the
collection seems a bit dated these days, you can't beat the grab-bag,
bizarre feel of it all. Takes me back.

MODE
is a virtual instrument that combines some of the usual analog-style
synthesis with  unusually sophisticated time-synced delays and
effects. Five (count `em) plugins in one.

Both products are US$199, shipping now.