From Jeremy Marchand:
Hobiconer lets you compose, import or export icons in many formats : Apple icns, Microsoft ico, CandyBar iContainer, bitmap (png or tiff). Features:
Compose your icon by simply dropping images on a representations (optional copy to other sizes).
- Compose quickly : drag multiples images at once with different sizes and then the app will complete all sizes by choosing the image that best fits each of them.
- Manage several icons in one project.
- Batch import and export .icns (512x512 MacOSX Leopard), .ico (Windows Vista 256x256), .png, .tiff and even iContainer files
- Use created icns directly in finder's inspector.
- Background color selector to check the appearance of your creation in different context: luminosity mode, custom color, transparent (checkerboard)
- Built in dock preview.