I found this website the other day and I think its great.
Information on walking/hiking/trekking here is the UAE is sparse to say the least but Christine has done a great job on the information and descriptions of the 4 hikes currently listed on the site. I havent done any of them yet but I definitely will once the weather cools off.
Check out the site for yourself and see what you think www.uaemountainsandwadis.com
Ian Ganderton 
Hi Ian. I think this site has moved to http://www.dubaihiking.org/