filetype set icons - Google Search
File Type Line Icons | Document, Music File, Code File, Powerpoint, Video File, PDF and Image Icons
Codeanywhere File Type Icons by Unity
Building a web app? Then this free, open source file-type icon set from Teambox might be just what you need. It includes icons for a ton of different file types, including TXT, RTF, WAV, MP3, XLS, CSS, HTML, DOC, PDF, AVI, SQL, and many more.