This is a great site, http://www.cs.usfca.edu/~galles/visualization/Algorithms.html
Has both interactive B and B+ Trees,
http://www.cs.usfca.edu/~galles/visualization/BTree.html
http://www.cs.usfca.edu/~galles/visualization/BPlusTree.html
I implemented the B-tree described in CLRS in JavaScript: http://ysangkok.github.io/js-clrs-btree/btree.html
To get started, press “init simple”. Then place your cursor in the input field just before the insert button. Now enter a number which isn’t in the tree and press enter. Focus remains in the field so that you can insert multiple entries quickly. If you push “delete”, this will be the action triggered when you push enter.
Suggestions very welcome.