Paint.NET alternative for Mac OS X I would be extremely grateful to anyone pointing me in the direction of the Mac OS X analogue for the free Windows image-editing software Paint.NET.

Basically the way I use it is I take lots of screenshots for work, then put arrows in there, some ovals and text - it's all for documentation purposes - mainly for Confluence.

The feature I can't live without is the arrows - they have points where you can easily curve them creating a very good visual e.g. for tutorials.

And of course it's great that you can do all of that in a lightweight app, couple of clicks manner.
You can use builtin Preview.app for adding arrows, shapes, text, magnifying glass etc. It's not as lightweight as Skitch mentioned by @jherran, but does the job You need.