Wikispaces are among the most reliable resources of educational technology tools. I am personally a huge fan of these web tools and I have created three wikis all of which are geared towards the use of technology in education. There are also several reputed wikis created by other educatos that are really a must for every educator to know. I am actually working on a presentation that will feature the top educational wikis and will soon post it here.
So apart from the tutorials created by educators such as me to help other teachers better use wikis no official tutorials were ever posted so far but this is not the case anymore. There is a Wikispaces YouTube channel that has just gone viral and that contains more than 25 screencast videos created by Wkispaces. The purpose behind this channel is to help users from all around the globe and show them how to utilize some of the useful features that Wikis have in store. I highly recommend this channel for you , you can browse it for videos and tutorials to share with your students. They need to know how to better use wikis and the best way to teach them that is through these videos.
Here are some examples of two videos I picked up fron Wikispaces Youtube Channel
1- Introduction to Wikis
2- Creatin educational wikis