True, you don't get the tasty part of the experience. But you also don't have to try to figure out how to hold the darned thing still and keep it from rolling all over the place while you're taking a sawzall (sp?) to it, either. I've made quite a few coconut toys for my birds to play in and, for the most part, I've come to the conclusion that it's much easier to buy the coconut thingies already made.
However, this is what I have found to be the easiest:
Select the shape/size coconut you want, whether or not it's scored so that it's supposedly easier to open realy doesn't matter.
Assemble the woodworking tools, go to the woodshop or go to somenoe else's woodshop.
Find a clamp or vice which is or can be fastened to an immovable object/surface.
Position coconut in clamp/vice in such a way that it is held securely and you have just enough room to cut off the bottom (or top or side depending on perspective) 1/3 to 1/2 (pending desired outcome)
The best thing I've found for cutting the coconut shell is a sawzall (sp?) or a dremel (sp?) tool with the proper attachment, but any way you try it's going to take a bit of time to get through the dang thing
Something I've thought about since the last coconut toy I've made is that you could probably rig some way to feed the nut through a table saw with the blade raised as high as it can safely go. In this case, I would probably attach said clamp to a piece of scrap wood, clamp the nut in place, and adjust my depth guide board so that I could drag the coconut across the sawblade to take off the right amount from the bottom using the board as a sort of handle.
EDIT: Got too carried away with how to cut the darned thing that I forgot to say that the easiest way to get the meat out is by scoring off small sections of it and scooping it out (very carefully, cutting it seems to make it extremely vulnerable to pressure applied to the sides, making it splinter occasionally) or letting it set out to dry for a couple days and then scooping it all out as it dries and separates from the shell. You might not want to eat it after the drying out option since occasionally it will mold if the weather's humid, but a little vinegar and/or a good hot water bath take care of that. You'd probably want to give it a really good hot water bath anyway if you're poutting it in an aquarium since coconuts have quite a high fat/oil content. I've only ever used them for birds so I've never bothered unless it started to mold. The birds love to eat the coconut meat, too.