ARadicalSimp by Walter Kissach is a free app that has both an instructional part and a calculator to help students learn to simplify radicals. This app covers both radicals and quadratic equations in detail. Each section comes with a guide which is actually an indepth explanation of the material that is presented in small chunks.
Each sub section has examples and a calculator that breaks down the radical into its exact answer with the radical sign rather than giving a decimal approximation.
I like this because it reinforces the idea of using radicals. Yes, I know people are using decimals more and more but I keep trying to have my students understand that most radicals are irrational and not rational
The calculator shows the actual break down from beginning to end. This is a way of reinforcing the material. I know my students are going to pretty much just copy the answer down but I plan to require them to include a small write up explaining the process. It might look something like this
"124 is 4 times 31. You can take the square root of 4 and it is 2 so it moves outside the radical sign and the answer is 2 times the square root of 31." I hope this makes them slow down and actually look at the material.