Personally, I'd recommend a Stumpjumper. Out of the box it is a very nice bike. I have about a 1/3 of one sitting in the basement that I totalled about 5 years ago. She gave me maybe 5 years of trouble free abuse and was only killed off when I crunched her into a tree at about 35mph. I no longer have the health insurance to allow me to ride.
I have a Hard Rock that I picked up as well. Was a $300 bike maybe 10 years ago. It too has been fairly touble free considering the cheap parts that make it up.