There are a lot around. If anything, most of them aren't that useful.
It won't be helpful immediately, but something I would recommend is to start experimenting yourself. Start small, say, by cropping images or making small edits with Paint (it's surprisingly more flexible than you'd think).
Once you've got the hang of it, try out Paint.NET
(essentially an upgrade of Paint, with layer functionality and some other features), and then start experimenting with GIMP.
It's a bit time consuming as a process, but it's also a lot of fun.
Just remember: always edit copies of a certain image. You don't want to ruin something important when you're fooling around