Here's a selection of some great Debian related sites. Many of these authors have been kind enough to credit me with an incoming link to my own humble efforts at some point in the past, and I'm pleased to now return the favour in kind and recommend their sites.
http://www.debian-administration.org
My personal favourite, Debian Administration has an active community who submit their own articles. There's a useful comments system where you'll always find further discussion of the topic readily to hand.
Surely one of the most comprehensive Debian HOWTO sites, I have often found this one useful myself on countless occasions.
A well known site with a wide range of HOWTOs for Debian and other distributions. The site's “The Perfect…” series of HOWTOs are particularly authoritative, but tend to be quite long so this site is recommended if you prefer a more verbose guide.
An easy to use site with a collection of original HOWTOs. The site's particularly well suited for users who are new to Debian or Linux in general, and the diagrams are a nice touch.
The site syndicates feeds from an amazing number of Debian blogs. Of course the quality of the posts varies, but your sure to find something of interest. I have my own RSS feed, but I'm not sure how to get syndicated…
http://riseuplabs.org/grimoire
Not really aimed at newbies, but more experienced admin's will find this author's notes to be well informed and clearly presented.
http://workaround.org/moin/Welcome
Recommended specifically for his excellent virtual mail server HOWTO, this site would be a good alternative to my own Postfix notes if you prefer a more verbose style of HOWTO.
If you know of any other useful Debian sites (or blogs) then drop me an email and I'll link to them here. If you feel like linking back to me in return then that would be very much appreciated. Thanks, Andy.