While building larger structures with struts and joints like these:
http://www.thingiverse.com/thing:9359

I find that I need some more tesselation of the structure.

This set of things forms a simple joint which allows you to easily form more triangles within the boundaries of your structures. Of course you can do a whole lot more than just form more triangles, but that was the initial intent.

These things derive from a couple of things:
http://www.thingiverse.com/thing:8130
http://www.thingiverse.com/thing:8129

If you're doing a permanent structure, you could still use thing 8129, and stick a 1/8" pin into the hole.

There are a couple of key design aspects to these things.
1) They are symmetrically paired, which means you can place two next to each other (the 'half' form) and they will allow their struts to be at the same level. In fact, the interlocking nature of the pieces ensures that once you have two collars on the rod, they will not slip easily. That alleviates the need for any type of fastener for simple installations.

2) They use nipples and dimples for grabbing. So, you don't need any extra hardware to bring the parts together. No nuts and screws to fiddle with.

There is a notch on both sides of the receiver to help facilitate sliding the nippled grabber into place. You can fiddle with the depth of those notches, or eliminate them completely if you find you don't need them.

If you have enough of these placed around your structure, a plain wooden structure suddenly becomes strong enough to hold a blanket on top (on a dodecahedron with 36" struts). If you are using shorter struts, like 24", then you probably don't need these to reinforce the corners, but can do other things instead.

The connoisseur of platonic solids, and other forms of interesting solids, will recognize the fact that truncated forms are easily formed using this system. Just don't use the stellated vertices, move these to the ends of the struts, put a cap on it, and there you have it! At least for some forms.

At any rate, you might find some use for this set if you're into building things with sticks.

1) Print equal numbers of receivers, and grabbers.
2) Slide a couple onto each end of a strut
3) Slide shorter struts into these for support, or whatever
4) Rejoice!

By default, these pieces fit on 5/16" wood dowels. You can easily change that by changing the gRodIR parameter in the file, and regenerate. The fit is relatively loose (10% larger than radius). If you want a more snug fit, make that more like 5% (smaller if you want it to be downright hard to move).

The best plan for keeping them in place, with friction, is to just put some blue tape on the rod at the point where you want it to stick, which will thicken it up just enough at that point.

If you want a permanent fit, then put a dab of glue in place right before you slide the piece over it, and that's that.