I've found specifically these ones: á, à, â, å, ä. I believe they COULD be used in the English language, or root ones such as Celtic & Germanic, but I don't know how they are pronounced.

Oh, and I've glanced at the articles [What does the grave accent mark on words mean?](https://english.stackexchange.com/questions/35347/what-does-the-grave-accent-mark-on-words-mean) and [Diacritic](http://en.wikipedia.org/wiki/Diacritic) if that helps jumpstart you on your assistance. Thank you, and *please* give examples of how they are used!