How I Use It
I first came across this site when doing some work with students on historic conflicts. BBC has a collection called The Road to War 1935-1939; the collection includes great clips documenting some of the events that led to official start of the war. Most are pretty short and effectively summarize for students the many incidents on the road to the conflict. I introduced one to the students as a whole group and then asked them to specialize in pairs, viewing the different clips and then doing a bit of extra research to become 'experts' on several of the different incidents.
Then as a whole class we linked them together to see how the pieces fit together. We attempted to analyze and see at what point conflict could have been avoided while also trying to salvage some kind of peaceful co-existence. It made for interesting discussion with many different student references to the source materials, something that I love to see in the classroom as it grounds opinions in evidence.
The site as a whole is very eclectic in some ways with a huge variety of topics AND quite a bit of variation in quality of materials. This has some real advantages in that I have had students pursue more obscure topics on their own (e.g. The Time When Americans Drank All Day Long and What Is the Point of the Commonwealth Today?) but also some drawbacks (you can't necessarily count on using the site). The collections (like The Road to War) are the best part of the site for sure.
If the site 'matches' something you are going to study in your class, it can be really effective. You just have to do a bit of research to see if the quality of the materials is suitable for what you are doing in the class (but you often have to do that). It's really best for giving students the opportunity to explore and learn independently around a theme or topic.