Cremation is all the rage in the funerary world, accounting for one-fourth of U.S. interments in the year 2000-a number expected to rise by another 15 percent in the next 10 years. Consequently, alternative cremation services are popping up everywhere. Houston-based Celestis will rocket your remains into space. Celebrate Life Inc. of San Diego will send you off in a lavish fireworks display. And, for somewhere between $1,500 and $3,200, Eternal Reefs, a Decatur, Georgia, company, will mix your ashes with concrete and turn you into an artificial reef on the ocean floor.