technique - Word Clouds and Phrase Clouds

I'm familiar with word clouds (or tag clouds) as used on blogs or on sites like Delicious. It seems to me that a tool similar to that could be of use to writers like me, who don't have an editor, when trying to identify typical or overused phrases. So here is my question:

1. 
   

   Does there exist an online tool which analyzes text samples for repeating phrases?

   
   


2. 
   

   What tools or techniques can a writer use to avoid recurring phrases or idioms too often?