Ive got the v700 which i think does a good job. It isnt cheap but can do medium format as well. I think the cheaper v500 can only do 35mm and medium format (?) so this might be an option if you have no large format to scan.

I have seen a contraption where someone used a dslr to 'scan' slides/negatives. From what I recall they use a tele lens with extension tubes, but i think a macro lens like the 60mm macro would work very well due to the purposely built flat image it produces. If you could get a good system going it would be much faster than scanning.