The Dragon and Chips series

Humourous Fantasy Writers - Terry Pratchett

Terry Pratchett's home page

Terry Pratchett discussion forums

You can also check out the Terry Pratchett Usenet groups - alt.books.pratchett and Terry himself posts on them from time to time. (I recommend a dedicated news reader like Thunderbird or XNews)

There's also a Terry Pratchett interview in issue 17 of Andromeda Spaceways Inflight Magazine.