Best way to convert text files between character sets?

Question

What is the fastest, easiest tool or method to convert text files between character sets?

Specifically, I need to convert from UTF-8 to ISO-8859-15 and vice versa.

Answer 1

As described on How do I correct the character encoding of a file? Synalyze It! lets you easily convert on OS X between all encodings supported by the ICU library.

Additionally you can display some bytes of a file translated to Unicode from all the encodings to see quickly which is the right one for your file.