Here at EmergingEdTech, we're big fans of the work our friends at AppED Review are doing*. AppED Review has been reviewing smartphone and web apps using this Comprehensive Evaluation Rubric for Assessing Instructional Apps since 2012. They've reviewed hundreds of smartphone apps, and added web apps to their process a couple years ago (they recently completed their 200th web app review).
Stop by and check out their reviews of apps that you might be considering, and explore their site to find highly rated apps for your classroom!
*Disclaimer: I am also on their Board of Advisors (an unpaid position). I have not received any compensation for this or any other post or page about AppED Review (I just genuinely respect the product and service).