The American Federation of Astrologers publish fabulous books themselves and they are also distributors for The Wessex Astrologer in the USA. Find them at www.astrologers.com.
The Astrological Association of Great Britain run a conference at Wyboston Lakes every September, as well as publishing The Journal every two months. Their website is full of all kinds of resources for astrologers, wherever you may live in the world. www.astrologicalassociation.com