I am exploring the creation of a delta bot and I need a triangle shaped thing as a base to hold onto tools.

This thing is a simple triangle base that can hold something. It has notches in each of the sides which can mate up with the notches on something like these keyed spans: http://www.thingiverse.com/thing:5867

Although the notch dimensions are different if you go with the defaults.

Not that you need to fit that span in the notches, but you can stick the key/notch on any of your designs. If you like epoxy, once you notch something in place, it's probably fairly permanent, and stronger than the rest of the plastic.

Also of note, since there are three notches, and if you make the keys a snug fit, the first one will go in easily, as the plastic will flix to fill the open notch spaces. The second one will be tighter, and the third will likely be downright hard to get in. This is a good thing if you don't want to use any fasteners or glue as the notched objects will stick fairly well just by the binding friction.

The thing is parametric. You can reconfigure the size by changing a single value which governs the length of the sides. The default is a 3" side, and 8mm thickness. Since the notch is 12mm wide and 12/goldenratio deep, 3" is about as small as you can go with that notch size, unless you decrease the size of the tool hole in the center as well.

There are M4 holes near each of the corners for your mounting pleasure. Of course, you can always provide more holes.

The really interesting part comes as I think about the little attachments I can stick in those notches.

As a bonus, if you're getting into OpenScad, but not too great at triangle math, there's a little bit of simple math in there, like finding the circle that fits within a triangle, finding the center of the triangle.

UPDATE: 29012011
Added truncated version of the platform, saves on plastic and gives 3 more flat surfaces.
Added OpenScad file, which is nice a clean and instructive

1) Decide on the size of tool base that you want
2) Edit the OpenScad file to suit your size (or go with the 3" default)
3) Print the thing out
4) Attach interesting things into the notches
5) Rejoice!

The key line to change in the OpenScad file is this:
// Create a tool base with a 3" side
tritoolbase(3*25.4, 8);

change the '3' to whatever size base you want, preferably larger than '3'.

If you want to go smaller than 3, then you should probably also change this line:

// Now we can finally figure out a nicely proportioned hole sizeholeradius = radius/goldenratio;

to be something more like:

// Now we can finally figure out a nicely proportioned hole sizeholeradius = radius/goldenratio/goldenratio;

That is, divide by goldenratio again to make the hole even smaller