If you're a web designer you'll know useful icon fonts are. You can change their size and colour however you like and are a lot more versatile.
Only problem is most icon fonts are just rubbish. The icons aren't very good quality or they just have a bunch of useless icons which you'll probably never use.
IcoMoon can change that by enabling you to create your own icon font. You simply use their web app to choose icons from a huge list, so you can choose specifically the icons you want, then download them in web font format so they working in nearly all browsers.
It's a very useful service which I'll be using from now on. It's just a lot more useful being able to change the size and colour of an icon without having to do it all over again in Photoshop or Illustrator.