If you need to know anything about paladin tanking then Maintankadin is the place to go. While a place that's basically only a forum might seem lacking in general advice in the form of articles, the truth is that aspects of tanking change so fast that static articles tend to become dated very fast.
That's not to say there are not dated chunks of information on Maintankadin. There are, and they're all attributed with the time when someone wrote the advice.
The main sections of useful advice are Basic Training, Gear Discussions and Advice and Cataclysm Raids. For the five man farmer you could have some use for the Five man dungeon section, but due to the raiding progression of most posters on Maintankadin, it tends to be rather dated.
The main strength with Maintankadin is that it's likely to have an answer to just about everything you'd want to ask about.
The main weakness with Maintankadin is that it's (rightfully) renowned as the number one site for anything tankadin, and thus a partially dated guide will sometimes continue to be seen as gospel even when the information is no longer accurate.
Luckily most guides come with a changelog including the date when something was indeed changed. If the last date is prior to a patch you know has been added to the game, be careful.
You can ask questions and be pretty certain you'll get an answer, even though not maybe the same day you asked it. Note, though, that you are expected to have read the FAQ pertaining to each section.
Occasionally you'll get jumped on in an unwarranted way (even though more often than not it is indeed fully warranted). When you take flak with little reason it's usually a combination of a dated guide/FAQ, and associated multiple pages long discussions, and a responder who just happens to know that one of the posts during a chain of disputing posts includes the answer you were searching for.
My primary advice is that you get used to the site for a week or so before you start posting. A few of the other posters can be terse in the extreme, a few others take for granted that the in-house jokes are appreciated by everyone, but in the end basically noone is out to hang you out to dry.
Well, let me rephrase that. If you repeatedly try to actively make an arse out of yourself then we'll cooperate and hand it to you.
That said, pay that gold mine of tankadin information a visit.