We have tanned several deer hides in the past. Notice I said 'the past'
We actually started out using the old school brain tanning method like Native Americans used. There are several tanning kits you can purchase from taxidermy sites and catalogs, but they all involve a lot of tedious scraping.
You best bet (if you have the $) is to drop off the hide at your taxidermist and let him send it to a tannery. I'm not sure how much it costs, but in my experience the $ is almost easier to come by than the elbow grease and time it takes to do it myself.
rw