Quickly, before I am Jinxed:
DTS (Digital Theater System) is a digital 5.1 surround system (or 7.1 in DTS-ES) using 5 speaker channels and 1 LFE channel for cinemas and HT. It was debuted in 1993 on Jurassic Park (Spielberg was an early investor).
SACD (Super Audio Compact Disc) is a music-only format of 6 channels (the 5 standard channels plus subwoofer, LFE is not the correct nomenclature in this format). Currently only analog outputs are standardized, meaning a forest of cables between the SACD player and the receiver. A single-cable digital solution is in the works but has not been accepted as a standard yet. An SACD is a strange disc. It is technically a CD but holds 4.7GB of data, identical to a single-layer DVD. Pretty much a hybrid of the two. Currently there are only around 3K SACD titles released. Of course "only" is relative, 3k being about 10x my cd collection.
FYI DTS is analogous to and competes with Dolby Digital, which was developed around 4 years prior (per Wikipedia).
From Wikipedia, Google, and memory.
