How do I create a folder with an icon for Finder (like I do it with the Dropbox installer)?
It's also interesting to know, how do I do it as user - not a programmer? Are there any tools for that?
Now that the Finder is using gray icons in the sidebar, it doesn't pay attention to a folder's custom icon. Some folders, like Applications or Desktop, get special icons because the Finder knows they're special, but there is no way to tell the Finder about new types of special folders. I'm fairly certain Dropbox uses a code injection hack to force its own custom icon.