Here is a conversion that I did and ended up giving to my cousin.

My dad and I bought this Univega on Craigslist for $40. I took the v-brakes off and put them on my dads bike and then started tinkering. I had most all of the parts laying around (including the drop bars and brake/shifters). What I ended up with was 1x7 gearing with a range of 33 to 84 gear inches. Overall, it's just a good beater bike that is relatively comfortable and utilitarian.

http://img.photobucket.com/albums/v2...ps24e8ab44.jpg

It's not a mountain bike, but a hybrid of sorts. Swapped out everything but the frame with a mish-mash of components--6600 crnaks, 105RD, 3500FD, Short4 cantis, Sora 3x8STI's. Just recently got a shortened stem and narrow 40cm handlebars.

Like someone wrote, a size-smaller frame is ideal; this one is a size smaller than what I normally ride, so it works well.http://bikeforums.net/attachment.php...hmentid=458300

Here's a picture of mine. Lately, I've been considering adding a dummy brake lever on the right to gain another hand position:

http://i36.photobucket.com/albums/e2...nowcommute.jpg