PHP6 unicode core

Current standard for Unicode is 6.3.0 but I'm not sure just what version PHP mbstring is built around.

Simple starting guide to unicode at Unifoundry who also have some nice font software.

A nice crib sheet for all of this UTF-8 Everywhere and to support the case against UTF-16 which also applies to widestring. Useful article on cprogramming.com

Libraries found so far for processing UTF-8 encoded Unicode strings ( Unicode Library List )
ICU Bulky but should be the gold standard for conversions? ... see UTF-8 in ICU
UTF8-CPP C++ not C!
utf8proc has ruby version as well as C
MicroUTF-8. Not well supported, only one project member listed
Boost.Nowide extension to boost framework
librope substring function for UTF-8 strings
Quick Routine for counting characters in UTF-8 - actually counts code points?

Local copies of sources

Unifoundry Unicode Tutorial
UTF-8 Everywhere
Should UTF-16 be considered harmful
Unicode in C and Cplusplus What You Can Do About It Today
Sample Unicode Page

Software samples

Couple of useful blogs from Nubari Software
Using UTF-8 in WIndows Using UTF-8 as the internal representation for strings in C and C++ with Visual Studio
UTF-8 Code point iterator adapter A code point iterator adapter for C++ strings in UTF-8

PHP Functions for UTF-8 
Portable UTF-8 A Lightweight Library for Unicode Handling in PHP
Patchwork-UTF8 Extensive, portable and performant handling of UTF-8 and grapheme clusters for PHP
phputf8 UTF-8 aware library of functions mirroring PHP's own string functions. A bit old?