The Unicode HOWTO, Bruno Haible -- probably worth reading -- I haven't yet.
What Is Unicode? -- this is also a page on the unicode consortium website (IIUC) -- some specific pages recommended to me (in various contexts):
UTF-32 -- "This document specifies a Unicode transformation format that serializes a Unicode codepoint (from U+0000 to U+10FFFF) as a sequence of four bytes."
There is a thread on abiword-dev@abisourcePLEASENOSPAM.com with some good discussion titled "Re: commit: abi: UTF8String class" around Mon, 22 Apr 2002 03:07:21 +0100 (BST). Some posts are from Andrew Dunbar. ToDo: Look up the thread in the archives and get a URL.
There is a thread (or several threads) on discuss@enPLEASENOSPAM.tldp.org -- one post is titled "Line drawing characters in HOWTOs", dated Sat, 20 Apr 2002 00:38:00 -0700. ToDo: Look up the thread in the archives and get a URL (after confirming there is an archive).