Almost identical to the this icon set is the Farm-Fresh Web Icons which also includes 32x32 versions and 1000 icons

http://www.fatcow.com/free-icons/

Silk is a fantastic set. Been using it for years and haven't found anything more versatile.

Also recently came across the excellent (CC-licensed) Fugue set.

http://p.yusukekamiyamane.com/

Wow. That's an even bigger set. I had been using these, but neither set is as comprehensive as Silk:

http://www.tutorial9.net/resources/108-mono-icons-huge-set-o...

and

http://prothemedesign.com/circular-icons/

It seems the main site is down, but you can get them directly from GitHub: http://github.com/yusukekamiyamane/fugue-icons

Awesome! Thanks for that. Silk has been great but sometimes the icon I want just isn't there.

You could, I suppose, contract the author of the silk icons for the icon you want.

If I were a more cynical man, I might even suppose that was exactly the reason for producing a royalty-free icon set -- to drum up business.

Cynical?

What better way to show your skills to people who would contract you than to point at something as popular as his icon set?

I meant it jokingly. It's a brilliant advertisement, to be sure; I think that most people just see things like that as done strictly out of the goodness of people's hearts, and while that may often be true, I usually am inclined to believe the more self-serving aspect of it.

Not that there's anything wrong with it whatsoever.

How do you mean? His site hasn't been updated for 4 years. I don't know anything about the author.

This is the author: http://twitter.com/markjames

I wish I had been foresighted enough to realise that the icons were more than the occasionally useful result of a period of insomnia. The set was started because I could not find a good icon set to use in a system I was developing.

I have done almost no icon design since this set was released; The icons have garnered me some personal infamy, and I make a little from text link ads, but I would kill the site if not for the fact that people still appear to find the icons useful and reliable.

For personal work, I use the fugue set linked previously.

Silk is a good set, but it's true that it's very easy to recognize in the wild. I think it's a good stopgap before you pick something less-used, but if you want your web app to have a voice and a point of view from a design standpoint, it's better to go custom.

THe Silk, FamFamFam set are easily reconizable which might be the perfect reason to use them from a usability perspective.

Here's a much easier way to browse them: http://www.famfamfam.com/lab/icons/silk/preview.php

Be careful, though- these are the most overused set of icons. They're like the Comic Sans or Papyrus of icons. Like another commenter said, if you're looking for some less-used icons, try these two (free) sets:

http://p.yusukekamiyamane.com/

I think that's pretty misleading comparing Silk to Comic Sans. A more suitable comparison would be to something like Helvetica or Times New Roman. Ubiquitous and overused but still a dependable choice.

Or the LED Icon Set: http://led24.de/iconset/

(Though they look a lot like the Silk icons.)

Someone also tried to expand the set, and hosted it here: http://code.google.com/p/famfamfam/

I love silk icons! Really clean - I think we need to push for better standardization of icons though. There are too many sites where developers put the icons without text labels and I find myself mousing over hoping for a tooltop while trying to stare at a 16x16 icon to figure out what it is...