I used to use Gimp, and have done so for years, if you're looking for a powerful, easy to use and FREE photo program, Gimp is really on the top of the heap!
I use Adobe Photoshop CC 2014. For $10/month, it's really worth the price! Out of all the other photo editing programs I have used, this one has been the best! There is a trial if you'll like to give it a try. I think it lasts for 30 days or so.
I use Photoshop and my husband uses GIMP. I prefer Photoshop as that is what I learned to use first, and my husband swears by GIMP. They are both great, but GIMP is free whereas Photoshop is hundreds of dollars. =)
Most of the time I just use the photo software that came installed on my computer which is fine for basic cropping and adjustments. Once time I needed to do something fancy for a gift guide submission and used GIMP which is free and has lots of bells and whistles.
I use IrfanView for most of my editing, and occasionally Inkscape, mainly if I want to make a composite image from multiple photos. They're both free. :)