Here are some good free photo editing software to edit your photos. Photo editing software differ from image editing software as they provide specific features to edit your photos. Some of such features are red eye removal, tagging faces, and creating photo books and slideshows.
All the photo editing software mentioned here are completely free, and make it lot of fun to edit your photos.
Picasa:
Picasa is one of the most advanced free Photo Editing Software. It lets you manage your complete photo library, edit photos easily, and upload photos to Picasa Web Album. It also comes with Face recognition feature to automatically recognize and tag photos belonging to same person. Read Picasa Review.
Windows Live Photo Gallery:
Windows Live Photo Gallery is the free image editing software from Microsoft. It is a part of Windows live suite. It comes with easy photo editing features, and lets you upload photos to facebook. If Picasa did not have face recognition feature, I would have place Windows Live Photo Gallery at first position. One feature that Windows Live Photo Gallery has that Picasa does not is capability to create panoramic photos. Read Windows Live Photo Gallery review.
PhotoScape:
PhotoScape is one of the most popular photo editing software on my website. I think the reasons for that are obvious. PhotoScape provides very easy to use functions specific to photo editing. You can resize photos, add text to them, change their contrast, make them black & white, change brightness, combine multiple photos, and more. Read PhotoScape review
Zoner Photo Studio:
Zoner Photo Studio is full fledged free photo editing suite. It comes with photo viewer, photo manger, and photo editor. It provides one click solutions to fix common problems with photos, like, remove red eye, remove wrinkles from photos, add nice effects to photos, sharpen pictures, and more. It also lets you easily share photos on Facebook, and Flickr. You can tag pictures, and create panoramic photos. Read Zoner Photo Studio review.
Photo Pos Pro:
Photo Pos Pro photo editor is a commercial photo editor that recently became a freeware. Photo Pos Pro photo editor provides tools for precision repairing of photos. It comes with advanced photo editing features, and lets you add special effects to your photos. However, it does not have any feature to manage your photo library. Read Photo Pos Pro Review.
Hornil StylePix:
Hornil StylePix is another free easy to use photo editing software. It is actually a combination of photo editing and image editing software. It lets you draw pictures, resize photos, rotate photos, synthesis photos, sharpen/blur photos, remove red eye, remove dust, and much more. Read Hornil StylePix Review.
PhotoPerfect Express:
PhotoPerfect Express is a nice free photo editing software that lets you easily fix your photos, and optimize them. You can easily enhance images, and comes with full fledged photo editing features. Read PhotoPerfect Express Review.
Stoik Imagic Free:
Stoik Imagic Free is the freeware version of Stoik Imagic premium. The freeware version provides photo management features, and photo editing features. Apart from that, Stoik Imagic Free also provides video editing features. This is useful for simple video editing. Read Stoik Imagic Review.
Xtreme Photo Designer:
Xtreme Photo Designer lets you easily edit, retouch, design, optimize, and distort your photos. It comes with lot of photo editing tools, but makes it extremely easy to use those to edit your photos. Read Xtreme Photo Designer Review.
PhotoPlus SE:
PhotoPlus SE is the free version of PhotoPlus software from Serif. The free version offers some really cool photo editing features. You can enhance images with paintbrushes and airbrushes; rotate, add perspective, and skew your images; and add special effects to your photos using filters.
ArtWeaver Free:
Free version of Artweaver comes with basic photo editing tools. You can use various filters to fix your photos. One great feature of Artweaver is that you can record all the changes that you did to your photos, and can play them back later. Read ArtWeaver review.
FotoMix:
FotoMix specializes in mixing multiple photos to create a single photo. You can also change background of your photos. Read FotoMix Review.
Note: This list only includes the software that you can install on your computer, and does not includes any online photo editor.