I put the sleeves on the light table and shoot them with the DSLR, then invert them + levels in photoshop. It gives unusable results as far as "picture" goes, but it's a great, indexable reminder and it gives a fairly good idea of the tones...
This one is a bad example, it flares a bit in the side, but it gives the idea..
I have done the lightbox digital method also. I recently picked up a Epson 1200Photo scanner with transparency templates for 135, 6x6, 6x9, 4x5 etc and 4x5 light source from a local thrift store for $5.98. Downloaded the drivers from Epson and scan all my "worthy" negatives this way. It replaced a HP Scanjet 7400c that I got for $3.98. That scanner was just too slow. 99.9% of my stuff isn't worth the chemicals or the paper to proof. I find this scanning cost effective for amateur use.