Haven't got any of my own worth posting. Yet. Still developing.
But assume most would be familiar with
Noel Carboni's Astronomy Tools? I've had it for a while, still fiddling/learning.
Also found
this cool one at Astro Anarchy. Star removal. You have to read some of his tutorials to make sense of it, but looks like it has great potential. I had a lot of fun playing around with this.
Not quite astro-related, but there are some great, free, actions at
TheLight'sRight. I particularly like the
sharpening toolkit, and they have more than one, but also image resizer.