Well there's been quite a lot of Discworld stuff put out for TV in one form or another. I just chain-smoked the Hogfather TV series last night in fact, and it was pretty solid. Mr Teatime was good. There are 4 parts, each linked from the preceding one so its all easy to find. Its about 3 hours all told.
Wyrd Sisters and Soul Music have been done in animated form, The Colour of Magic, Hogfather, and Going Postal have been done as TV movies. A couple of Pratchetts other things have been done too (Truckers, Johnny and the Bomb), and several others are speculated (Sourcery, The Wee Free Men, Unseen Academicals, and The Troll Bridge (a short story)). Plus of course most of his stuff has been put out as audiobooks if thats your thing.