[jacquesm]

Here is one list of short .io names:

https://iwantmyname.com/blog/2012/05/100-shockingly-short-io...

and here is another:

are.io bow.io cot.io cry.io dew.io dip.io dye.io ear.io egg.io fee.io fry.io had.io hem.io hid.io hut.io jug.io lid.io lie.io lip.io men.io mop.io mow.io oar.io ore.io pit.io rag.io ray.io rib.io rid.io rot.io sod.io toe.io tow.io tug.io was.io won.io yaw.io

I did not bother to verify availability.

[bobwaycott]

This is from a few minutes ago: https://news.ycombinator.com/item?id=5663917

[muloka]

Ha you beat me to it.

[andyhmltn]

Just a note: That list may be out of date. I see my domain (fry.io) on there, and I registered that a good few months ago :p