I've tried several lightboxes, DIY, but they would collapse on me after a time (moving it around too much!)
What I've done now is freezer paper taped against the wall/table with a length of interfacing over it to soften the light and minimize reflection. My pics still come out dark sometimes, a side-effect from living in Oregon, land of no sun, but I just adjust the exposure in Photoshop as needed.
The nice thing about the paper and interfacing technique is I can just stack something on top of it and not have to worry about moving a big, tissue covered box!