As with any musical instrument that has a large number of enthusiastic players, there is a multitude of sources of information about bagpipes.
(Everything on this page is "to Follow!")
Books (including Tutors)
I have very few books about bagpiping - all rather lacking in detail about history and theory - but a quick search of Amazon or the British Library catalogue reveals that there is no shortage of scholarly treatises on the Great Highland Bagpipe and other varieties of this genre of instrument.
Some of these have come and gone but even those which have "ceased to be" can have useful articles (if you can find them on-line or in archives).
A few of the pages given out during courses have proved to be useful.
There are a lot of websites offering advice on musical theory pertaining to the bagpipes.
Some, listed below, have been invaluable to me in developing my understanding of bagpipe tuning.
The following list is limited to the UK. There are many regional societies in other countries devoted to the GHB and other forms of piping.
The Bagpipe Society
College of Piping
National Piping Centre
Double Reed Society
I have only attended one such event - organised by the Piping Society in London in 2012.