I just came across this free tool for Windows called Metro Studio 3. Basically, it's a collection of over 4000 useful icons that you'll probably use in an application and a simple editor for editing and exporting them. It's free and all the icons are royalty free, so you can use them in commercial apps. It literally has just about every icon you'd ever need in your application. Many of them are well known icons that people would recognize right away. For instance, the Display-Brightness, Drag 01, Favorites, Folder, File, Download, Mic-03, etc. icons are some that you'd recognize anywhere.
Take a look at this link to browse the icons:
The editor is really basic and might not be good enough for what you want, but you could easily export the unedited image as any format you want (png, jpg, ico, svg, XAML, etc.) and edit it in something like Gimp or Photoshop. The editor only lets you change the background and the icon color (the whole icon), so that's not very good for some icons. They're so basic and they come in black and white with transparency, so you can easily add color in an image editor.
Anyways, I hope this helps some of you guys that uses Windows, or at least owns Windows. I'm extremely happy I found this because I can think of so many times where this will benefit me. I don't have to spend time trying to make icons in Gimp that don't look too great. This has just about everything I need and they're all "standard" so people will know what they are. The first thing that pops in my mind is how great it'll be for making icons on a toolbar.
Here's the link to the download: