Best looking defence.

[LochNessCheeseBurger]

So I had this session on for 6 hours, and at some point I noticed that the outside bend of a transport belt moves faster than the inside bend. I thought it would make for some cool experimenting, and the rest is history.
Before fight:

After fight:

The great thing is that creepers don't attack transport belts, and so they just rush for the turret in the middle. Some do get through because of pushing and luck, but only one or two.
They also make for a cool illusion when you've got them moving.
EDIT:
I expanded it a bit more, so it's even harder to get into.

EDIT: Here it is built up some more:

[Aza-Industries]

Cool.
I've always thought about experimenting with this, more specifically just outside my walls with belts facing out.

I wonder.. if you put belts right next to turrets and a creeper gets to it can they attack it? or are they pushed away the second they stop moving to attack?

Man this game is great fun experimenting with.

[LochNessCheeseBurger]

I wonder.. if you put belts right next to turrets and a creeper gets to it can they attack it? or are they pushed away the second they stop moving to attack?

Unfortunately, they don't. I tried putting chests all around to see if they could break them or if they would get pushed away by the belts first, but they were able to destroy one. Possibly because there were creepers standing behind the one that got close, stopping it from going backwards. Anyway, even if they did get pushed back, they would have still dealt damage, because when you're running around with creepers following you, when one deals damage, it stops for a second, but it still dealt damage.

This set-up would be good for putting around walls, since it would stop creepers from attacking unless there was enough to push themselves forwards. The thicker the wall of belts the more creepers it takes, since if there's only one creeper then it will just get stuck on the belts, unable to advance.

Also, if you want to try it out, it's a sort of checker-board pattern. For my little platform, I used 4 'chunks' of belts rotated. So for my top right side, I used top-facing and right-facing belts, but for the bottom right side, I rotated it and used right-facing and down-facing belts instead. It would be great if multiplayer was here, so that I could show you the different discoveries I have made, and how to use them. It would make it so much easier to show you how to make these.

[FreeER]

It would make it so much easier to show you how to make these.

A youtube video should work nearly as well

[slpwnd]

Haha, fantastic:)