If you are the technical or administrator contact for a domain name then you can use DMA's domain opt out facility which (should) mean you get less junk email at your domain. The DMA is the Direct Marketing Association! (NOT Dayton Microcomputer Association).

There has been much consternation throughout the internet community about the DMA's adoption of opt-out rather than opt-in solutions to junk email. I suggest you read Nick Nicholas' article from mail-abuse.org which is reproduced here.
The original should be available at http://mail-abuse.org/anti-dma.html

Please read elsewhere to decide if you want to use there service!

This is a link to their service:
http://www.dmaconsumers.org/emps.html

The DMA also provide opt out lists for individual email addresses, telephone numbers and snail mail addresses.