Out of the options listed so far, I've used the black 3m Color Quartz T grade sand, Soilmaster Select Charcoal colored substrate, and Tahitian Moon Sand.
My favorite so far is is definitely the 3M Color Quartz. It is a true black and that is my main reason for liking it so well. It holds any plant and is inexpensive as far as "Plant" substrates are concerned, ~$20 for 50lbs. It is also inert so it shouldn't affect the water parameters at all.
Next would be Soilmaster Select Charcoal. This is very inexpensive at ~$15 for 50lbs and one 50lb bag is enough for a 75g tank. It doesn't hold plants quite as well as sand but as long as I use tweezers to plant, the plants don't come up. This is economically the best substrate in my opinion and if it were black instead of charcoal color it would be my favorite. While the batch I have seems to be inert some have claimed it alters their KH which is possible since this substrate is hygroscopic and absorbs the water along with whatever may be in it.
Tahitian Moon Sand is almost as nice as the 3M Color Quartz but it is a much finer grain size. I have had this in a 10g low light setup for about 2-3 years now and it works well but I probably wouldn't use it in a larger tank due to it's cost, ~$20 for 20lbs.
The Black Beauty blasting grit is also an economical substrate but may damage the barbs on Cory cats or the mouths on other bottom feeding fish and possibly shrimp. I haven't used this yet and probably won't. It's hard to say what the composition of this is since it is used as blasting grit.
This past weekend I got an look at the new Black Flourite Sand. It is about the same grain size as Tahitian Moon Sand and is priced similarly when you add in the shipping costs. A SWOAPE member will soon be replacing his Onyx substrate with the Flourite Black Sand so the Jury is still out on how that will work.
As with all substrates, I tend to choose them by their look first. I no longer consider any of the plant specific substrates like Flourite or Eco Complete any more do to their cost. Plants grow just as well in sand as they do in products marketed for planted tanks as long as the water column is fertilized. I prefer to use the money I save on substrates to pay for fertilizers and more plants
Re: Alternative Black Substrate? 
Overfloater thanks buddy, - it appears to be in the 2-3mm range, sweet 
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