The range of active crossovers now available seems to be expanding very quickly. Here is a list of some of the options available. If you know of any that I've missed, please let me know via the comment section below.
MiniDSP > (Low cost flexible PC controlled solution)
Behringer Ultradrive DCX2496 > (Popular pro choice for a stand alone box)
Ashly Protea 3.6P> (Similar to DCX, other crossovers available)
DEQX > (The ultimate solution)
Hypex AS2.100 >
CAD Audio DSP modules >
DIY analogue (ESP) >
Bodzio Sound Easy >
Thuneau Allocator >
So what do they do and how are they different? See my summary of active crossover options or jump to which one is right for me?