The Icon Library (google.com/design/icons) lets you quickly browse and export icons from the material design icon library, containing over 750 icons. You can export into formats that work well for the web, Android, or iOS.
The new Device Metrics Tool (google.com/design/tool/devices) lets you quickly look up screen specs like screen sizes in DP units, perfect for deciding on an artboard size for mockups. You can even sort by any metric, so you could see the full list in increasing physical screen size.
Check out our latest additions to our material design resources at google.com/design/resources, and let us know what other tools you’d like to see in the comments!