My own game, Deluxe Pacman has always been freeware. I started out making it as a PC version of the Amiga game of the same name (with the Amiga author's permission) for my wife who liked the Amiga game and missed it when I moved on to the PC.
I have two versions available for download, both made with Allegro 4 & 5. (actually 3 versions if you count the older DOS versions I still have as well).
Deluxe Pacman 1 & 2 are available on my personal website. DP1 is made with Allegro 4, DP2 is made with Allegro 5. And both have level editors. They're more than just Pacman clones, they have many more features to them.
This is a gameplay video I done up of DP2.
And you can download all versions here: http://home.cogeco.ca/~nroy15/games_index.html
(same as the link in my signature actually)
One of these days I will compile it up for Linux and other platforms.
Other software I like are 7ZIP, already mentioned.
Irfanview for image viewing, I have the 64bit version on now and it works great.
GIMP, free photoshop like image editor.
Some nice software I have used in the past to help with my game graphics was Tile Studio, a free tile editor that also had a map editor which I found handy for prototyping maps, testing how the graphics look and sometimes I edited with other packages then imported into tile studio to organize them into sprite sheets as you can define the size of them etc.
BLENDER is an awesome tool to create really nice quality graphics for your games and it now has tons of tutorials on Youtube to help you get the hang of it quickly (as does GIMP actually).
And of course, most of us know about Code::Blocks etc.
It's a lengthy list honestly. I try and develop my games with 100% freely available tools with no strings attached.