Other
Saskatoon Public Schools: Mental Math Strategies
Strategies for basic addition and multiplication are explained here and there are several practice worksheets that can be downloaded.
Khan Academy
Khan Academy: Add 10s and 100s (No Regrouping)
Practice solving problems like 344+20 and 344+200. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
AAA Math
Aaa Math: Adding Tens
This game helps you practice adding tens. You will get to see a percent score of the answers you have correct, as well as running totals of the answers you have correct and incorrect.