Online Image editors
Aviary
Color splash
28 online photo editing sites
Desktop editors
Gimp
Paint net
Image animation
Pictures to life
Blabberize
Lunapic
Gickr
Image addons for Firefox there are way to many addons to list but I will list the ones I use my self I suggest you read the very long list it may have uses you have been looking for and if a addon is incompatible with your Firefox browser I suggest you read my instructions on how to bypass that on my suggested Addons page.
Reverse tiny eye
Web slide show
Thumbnail zoom
Open image in new tab
Old Google Image search
Auto slide show
Free Online Image hosting
Photobucket
Flicker
Yfrog
Desktop host
Picassa
Fastone
Enhance photos
Riot
Fotosketcher