Heres a cool product I found on a German fly shop web site. These are not for the dry fly guys and some folks may cringe, but these seem to be a neat product nonetheless.
Heres a description from the website:
Unique, pre-formed body nymph from a combination of plastic and tungsten.
A great product, complete with brains, a strong chest and a segmented body. Can be easily integrated with three-thread or with a thin Dubbingstrang on the hook shank. The high dead weight, the use of lead wire or beads unnecessary. This body can be colored with waterproof markers or colored lacquer. Available in 8 sizes.