The Apple User Experience folks have put together a little kit to help
developers create Aqua-style icons;
<a href="http://developer.apple.com/ue/aqua/resources/AquaIconKit1.1.dmg.bin">grab it here</a>.
It's probably been there for a while, but I've only just noticed it. Don't get <em>too</em> excited,
though; it's just a set of Photoshop 7 templates and actions for folders, plugins and document icons.
Useful nonetheless.
Of course, what we <em>really</em> need is for someone to create an online repository of NSToolbar-suitable
icons, with keywords for each icon giving appropriate uses for it. PNG previews would be displayed, and you
could add icons to your "download basket". When you were finished, you could download all the icons you'd
chosen as TIFFs with transparency, automatically TARred and GZIPped for internet transfer. I'd pay for such
a service, as long as I gained unlimited distribution rights (within an app, obviously) for the icons I'd bought.