http://www.guardian.co.uk/styleguide – UK Newspaper
http://www.bbctraining.com/onlineCourse.asp?tID=5487&cat=0 – The BBCs Style Guide which is pretty good
http://www.chicagomanualofstyle.org/cmosfaq.html – The classic Manual of Style
http://www.timesonline.co.uk/section/0,,2941,00.html – Extensive guide from one of the worlds oldest and most respected newspapers.
These style guides have been hanging around on my hard disk for a while now, better to have them out here in the open, I’ll cross post this to www.coffeecritters.org as well. I hope they all still work OK.
If you have any other style guides post them in the comments and I’ll update this.