UnicodeChecker

UnicodeChecker is an application that displays information for every code point from the Unicode Standard.

For a given number, UnicodeChecker will display that character along with its UTF-8, UTF-16 and UTF-32 encodings, XHTML entity, Unicode Name, mapping information and much more.
UnicodeChecker features several conversion functions and other Unicode utilities, some of which are also added to the Mac OS X "Services" menu and/or AppleScript (e.g. converting text to and from HTML character entities, (un-)escaping Unicode for CSS or Java, getting properties via AppleScript) so they can be used from within other applications.