I too have noticed the demise of the non-suspension MTB. About the only alternatives I can think of are

1) Build one up from scratch. Since most frames are spec'd for suspension forks, you'll have to sub a suspension corrected rigid fork in. $!500 would be more than enough to build a killer bike.

2) Scour the area stores for old stock.

3) Find a good used one, either at a dealer or garage sale. If it has a suspension fork, swap it.

4) Go single speed. Its a whole new world and quite enjoyable. Jenson USA has the KHS Solo ('03) for a couple hundred on closeout.

5) Think about a cyclo-cross bike, if it fits your needs.