I have not found a single site online that I would recommend about necromancy. In general people just don't want to publically share their experiences and practices with this topic. Due to the fear and missunderstanding of the topic, as well as the dangers of a lot of the work.
I can recommend some good books on the topic however...
One of my favorites is Greek and Roman Necromancy by Daniel Ogden. This is a VERY good book on the topic, as well as having all of the important points referanced.
Forbidden Rites, a Necromancers manual of the fifteenth century by Richard Kiekhefer. The only problem with this book is that a lot of it is in Latin. Still worth the read though for the amount that is in english.
If you want a quite different approach to necromancy in the author's very own style, then check out The Necromantic Ritual Book by Leihlah Wendel
Another approach is to read the historical records of famous necromancers from old texts. The Greek and Roman Necromancy is a great place to start for referance material. Another helpful area to look into are some of the better books on spirit communication in general, yes most are cheesy and newagey, but there is the odd good one out there.
The best area to start with necromancy is to work with your own ancestors. There is a lot of information about working with your ancestors on internet sites as well as books on Vodou and Santaria.
Best of luck in your search (IMG:
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Athena