Apart from Joel's article on the subject, where can I find information to help me get a deeper understanding of Unicode?
- Unicode Home Page
- Character Sets And Code Pages At The Push Of A Button
O'Reilly has a fairly comprehensive book called Unicode Explained.
Maybe, this Wikipedia article.
Joel Spolsky's The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) is pretty much essential reading. It's clear, sensible, good quality, and points you in the right direction for further reading.
I have a fairly lightweight "Unicode for .NET folks" page. It's almost certainly got nothing on it that you haven't seen elsewhere, but maybe explaining things a different way will help a bit.
The UTF-8 and Unicode FAQ for Unix/Linux has a lot of useful information on the subject. Although it's meant for Unix/Linux users, most of it is not platform-specific. The FAQ also lists many useful references.
For a programmer, I recommend the book "Unicode demystified" by Richard Gillam (Addison-Wesley).
Korpela's book, mentioned by Bill the Lizard, is more targeted toward users (programming is in chapter 11, a bit short, IMHO).