I've prepared a little quiz about Britain. If you know your pints from your pickles, you will surely be able to amaze your friends with your scores. And if you don't then, hey, you can just not tell them your score.
The Septic's Companion is an A-to-Zed dictionary of British Slang words and phrases, written by a Scotsman living in America. You may know it better by the title it had for the previous ten years, "The English-to-American Dictionary". The online dictionary is all free; the book contains all that and more riveting British stuff.
I mentioned the book, right? It's a lot more portable than the website, so you can enjoy it in places your iPad won't go.