Personally I don't want a whole bunch of engines playing on here. I have Fritz and if I wanted to play it I would play it on my computer. Anyway you don't learn much by losing to a computer (assuming you're not a titled player). They don't play the same as humans and it's a completely different style of play to do well against them. You'd probably end up doing more harm than good trying to get better by playing them.
I'm not saying engines don't have their place in chess. Analysis by computers can be a great help (tactically not positionally) and GM's use them to help make sure they haven't missed something in preperation. But really when you could play any number of real people why would you play a computer?