Almost identical to the this icon set is the <i>Farm-Fresh Web Icons</i> which also includes 32x32 versions and 1000 icons<p><a href="http://www.fatcow.com/free-icons/" rel="nofollow">http://www.fatcow.com/free-icons/</a>
Silk is a fantastic set. Been using it for years and haven't found anything more versatile.<p>Also recently came across the excellent (CC-licensed) Fugue set.<p><a href="http://p.yusukekamiyamane.com/" rel="nofollow">http://p.yusukekamiyamane.com/</a>
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.
Here's a much easier way to browse them: <a href="http://www.famfamfam.com/lab/icons/silk/preview.php" rel="nofollow">http://www.famfamfam.com/lab/icons/silk/preview.php</a><p>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:<p><a href="http://p.yusukekamiyamane.com/" rel="nofollow">http://p.yusukekamiyamane.com/</a>
Someone also tried to expand the set, and hosted it here:
<a href="http://code.google.com/p/famfamfam/" rel="nofollow">http://code.google.com/p/famfamfam/</a>
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...