In my gmail account and on my horde online filter to limit the amount of kinda-spam, (email newsletters I am unable to read all the time or dont have a high priority and I dont have enough time to unsubscribe or am unwilling to change my email address) I use the following filter rules that search for body text filtering email most likely to be automated newsletters to aLists IMAP folder.
The following words are what I filter:
unsubscribe
reply with remove
"to be removed"
subscriber
enewsletter
no longer wish to receive
"to stop receiving"

In the to: field
undisclosed

This filters most of my newsletters into a lists folder for later review and reading when I have the time

I wish I could run a separate spam filter like tool that could learn newsletters from my normal mail and spam.

Anybody have any other filter word suggestions?