Look past the simple appearance and you can find a great geometry tool.
Community Review for Math Open Reference
This has the potential to be an absolutely wonderful tool. It is not there yet. The website is an interactive geometry text book. Originally designed for high school, it is easily used in lower grades to introduce a wide variety of topics. You have to be careful to avoid the ads that look like they are part of the site. There can be a lot of them. I also got one about how to improve your abs. While possibly helpful in its own way, not helpful during a classroom introduction on angles. The great part is that for a topic, you will get an interactive model, key vocabulary with definitions, demonstrations, possible extension ideas, and related topics. The interactive models, in my opinion, are the biggest asset of this website. They will give students visual models of the topics that they can move around and see how the vocabulary is related. For example, when introducing angles, the model lets you move around the angle and will give you the exact measurement as well as the type of angle (acute, obtuse, right...) as you move it. If they can get rid of the ads, or make them more appropriate, this could be a wonderful teaching tool that would be available to the students anywhere that they can get online.
How I Use It
While this website is originally designed for high school geometry, with the adoption of the common core, it can be useful in any geometry lesson. The website is basically an interactive geometry website. It lays it out very simply and gives demonstrations, interactive examples, definitions of core vocabulary, and related topics. Some lessons even give extension ideas to try out. The students will really like the interactive part where it gives a visual model of the vocabulary. It is very easy to use. The bad part of it are all the confusing ads that you will run across that look like part of the website but will lead you to other sites.