Is there an organization who repackages old LEGO bricks into sets to give to underprivileged children? Does Lego have a program by which we can return old LEGO parts so they can be reassembled into packages for underprivileged kids? My kids, and now grandkids, have always played with LEGO bricks and I have a large collection of parts, not in their original boxes and would like to give them to an organization who would reassemble them into workable sets for disadvantaged kids. I hate to just throw them away as I must have several hundred dollars worth of parts.. Any ideas?
Another option is to locate a nearby BrickLink vendor and request them to sell the pieces and donate the proceeds to charity. So far as I know, this is the best way to donate, as the pieces are sold for their appropriate value and the money can be donated as you wished. You may consider donating the pieces to Creations for Charity as well.

If you really want to donate parts, the best way would be to use the money from other suggestions to purchase general purpose block sets, and donate those.