Text characters frequency analysis online
Also a functional javascript approach example (code snippet available)
Analyse
This "online tool" basically counts how many times each character is found in the given chunk of text.
Output is presented in a comma-separated format and is sorted according to the frequency of characters (most frequent characters first).
As it is written in Javascript (mostly pure JS, with jQuery used for UI interaction), it does not rely on any server-side software and may be easily copied and distributed. Feel free to do so.
Also, for the sole purpose of madness fun, the script is composed in a somewhat functional manner. Moreover, not a single equals sign ("=") was used (optimising code with the given limitation is left as an exercise for the reader).
Code makes use of Array.map() and Array.reduce() methods, so it requires ECMAScript 5.1-compliant browser (most of modern browsers are).