I know its been a minute since you posted this but I was hoping you might give me some insight as to your findings.

I am using TinyMCE and want to implement a character count in the same manner you described (digg/twitter) that will show the "live" count as you type into tinymce.

Did you manage to get it working? and would you mind sharing with me how to implement this and if you run into any issues.

I iz Newbie...

Character countdown using observe_field.

i will test out soon, and hopefully report back on progress tonight.

valdiates_length_of :filed_name, :max => 500

However, the harder answer is how to make a dynamically updated character countdown appear in your view.  Like digg or twitter.  E.g., 69/500 characters left. 

Maybe i'm just an Ahole, and google hates me, but there has to be some sort of scriptaculous script/method that people use, shouldn't there be since rails is now at least 3 years old?

i found one with some joker using jquery, but i already use scriptaculous and prototype throughout my project for other stuff.

thoughts?

   I am using TinyMCE editor for textarea.how to limit the characters in that textarea.
   500 is limit for that textarea,how to limit characters for this textarea in client side.

   alert message after 500 characters or displaying dynamic count of characters above the text area.

thanks,
Ravi.