My first thought is to do a weekly-ish email with resources, both general and subject-specific. Here's this week's:
ViewPure - showing a YouTube video in class? If you input the url in ViewPure you get a nice clean screen (no ads, no sidebar) to display.
Public Domain Review - a collection of images, books, essays, audio recordings, and films found in the public domain
Plickers - A low-tech way to collect student input. Each student gets a "paper clicker" barcode to indicate their answer. You use your device (android or iOS app) to collect their data. You can even see a real-time bar code of answers and see individual student data.
Flipped Classroom Tools - If you're flipping your class (or thinking about it!), check out these 7 tools.
Random Name Picker - a fun colorful wheel that you can use to randomly choose students in class
Map Making Tools for Students
Assessment Resource Center for History
An Interactive Map of the Napoleonic Era
Human Footprint Interactives
Using trendlines in Google Spreadsheets
(If you're wondering, I found these sites either on Twitter or on Richard Byrne's Free Tech 4 Teachers blog.)