I've been studying up on medieval archery for the past several months and just ordered my first "D" style English longbow.
http://www.woodbows.com/lelb.htmlI'm an inexperienced archer, so this is going to be a hard way to start, which is why I chose a very inexpensive bow to begin with. (Some of the yew, lemonwood, etc bows can be very expensive!)
Anyway, to get to the point, there is an organisation in the UK called the British Longbow Society, the purpose of which is to educate/train/compete using the same weapons and traditions from the middle ages. Unfortunately, there does not appear to be a US chapter. If anyone out there knows otherwise or is aware of a similar organisation, please let me know.
Here in the US we have a few renaissance groups with similar interests, but by and large they seem to encourage wearing tights, hose, and feathered hats. No thanks.

Edit: my particular bow is 72" and draws 53lb at 28".