Midtone design studio provides this set of icons  free for use in any project.

Even if it is a little offtopic, I want to say that I really like the design of this site. Midtone Design Studio belongs to Jonatan Castro Fernández, a spanish freelance graphic and interface designer who lives in Ourense, Spain. 

Update with some new icons

I love these icons from Midtone too – they are free.