I'm a fan of paint.net, it's easy for me. I do notice that there are photoshop people and paint people though, and even some gimp users out there. But for those that use paint.net, I found some plugins that have been useful lately, and fun, on this site here:

http://forums.getpaint.net/index.php?/forum/44-plugin-packs/

I have downloaded these:
Very useful - http://forums.getpaint.net/index.php?/topic/32048-boltbaits-plugin-pack-for-pdn-v406-updated-august-9-2015/
Very useful - http://forums.getpaint.net/index.php?/topic/18968-shape3d-2007-08-24/
Downloaded but not used - http://forums.getpaint.net/index.php?/topic/16607-blendmodes-plus-v235-32410/

Edit, another good one:
Alpha Blend and more - http://forums.getpaint.net/index.php?showtopic=11619

Edit [4-14-16]
This one will allow you to use paint.net to open photo shop drawings, psd, and save as psd as well.
Paint.NET PSD Plugin - http://psdplugin.codeplex.com/

Ton of extra effects
MadJik's plugins - http://forums.getpaint.net/index.php?/topic/7186-madjik-all-plugins-last-updated-2012-01-01/

I personally don't own PS, and use Paint.net This is quite helpful indeed, thanks for sharing!