A useful resource for Icon Semiotics comes from the Graphical User Interface Gallery site run by Marcin Wichary. The site is an "online museum of graphical interfaces" (especially old and obscure GUIs) and allows you to see how the GUI has (or has not) evolved over the years. Of particular note is the interactive chart of icons from various interfaces which features many visual representations of applications, settings, and system functions.
Another Icon Semiotics resource comes to us from Ro London. His site showcases 300 icons from 1800 web sites and includes examples of arrows, comments, documents, email, and print icons.