If you are like me and every now and then develop applications that you want to create an icon for, and you don't have the money to spend on a nice commercial tool (or rather spend it in Halo 3, RockBand or Guitar Hero III), then you probably face the problem that tools don't tend to support saving bitmaps as icons.
In the past I was using the old icon editor that came with mhh… was it Visual Basic 3? and life use to be good cause back then, icons were mostly used at 16 colors and you mostly cared for 16x16 or 32x32 sizes and the tool was decent for those scenarios. But now that icons can use thousands of colors and that you can use up to size of 256x256 it's certainly not a professional look icon when all you have is a 32x32 16 colors icon.
So then I decide that I was going to build my own icon editor and started coding it in managed code, at the middle of it I was looking over the internet for the icon format and sure enough I was reading all the details of the format, headers, API's, etc, when suddenly searching for a specific struct yield a result that basically stopped me from doing any more code.
Basically there is a sample in MSDN that has all the support that I need.
It supports creating an icon, adding multiple formats to it such as 16x16 - 16 color, or 48x48-24bit color, up to 128x128-32bit color. It then allows you to import a bitmap into them and mark the transparent colors (XOR Mask and AND Mask) and everything. Additionally supports extracting icons from files, although I'm sure it could do a better job with PNG compressed files and other stuff, it's still million times better than my old icon editor.
Nice thing it even comes with the source code in C++ in case you are interested on learning more about icon files.
The article is from September 1995, but its still great.
The code and executable can be downloaded from here:
Disclaimer: I do not know how good or bad is the source code nor I pretend to recommend it against any other commercial tool, I'm just saying that its good enough for my "hobbyist" projects and you might find it useful.