Q:

Automatic stress marking of Russian text

I'd like to be able to take any piece of Russian text and have the stress marks automatically added.   I think this would be a useful tool for learners but I can't find a site that does this.   Is there one out there?   If there isn't I'd even consider creating one and would welcome any ideas about how it could be implemented.   

A:

Try russiangram.com.   It's free and does exactly what you want: add stress marks and dots above the letter Ё.

A:

Not an online application, still:
RussAcc

Программа RussAcc предназначена для озвучивания текстов, создания аудиокниг (в формате wav, mp3, amr, aac + плейлист m3u), расстановки ударений (Nicolai, Alyona, Loquendo) в русских текстах (отсюда и ее название - сокращенное Russian Accents), удобного чтения книг с экрана.  Можно использовать RussAcc как редактор текста, конвертор FB2 в TXT.  Заяц русак, как известно, способен быстро ударять по барабану, RussAcc же очень быстро расставляет ударения в текстах. 

Just in case: I'm not affilicated with them, but used the tool some time ago, seems to be quite nice (except for the edge cases). 

A:

http://www.grammatica.eu/ is probably the best software of this sort, and the upcoming second vesion should make it even better.  It's quite expensive, but I can highly recommend it.