This isn't a super new post on the holy paladin blog community, but this a question I've been asked so I'm just using this blog to answer it. Perhaps it can be useful for someone else :)
There are several very good gearing guides that have been written by fellow paladins when Naxxramas was still new. If we're a few content patches later now, little has changed on the gearing side pre-raid, but mostly the argent tournament.
The guide I'll site mostly don't include that, so you can go there and give a look to the rewards in case some of them look cool. The Titansteel Spellblade has been added too, but is a dagger (I guess so that shadow priests can use it). The Titansteel Guardian is still the best for paladins, despite its nerf some time ago.
My best gearing guide pointer will be Banana Shoulders:
Pre-Raid Holy Gear Guide
Gemming Your Holy Paladins
(I don't completely agree with Siha as she's a spell power addict, I'm an intellect addict, so I gem for +16int gems on my yellow slots, for example. It's mostly a question of having enough mana or enough hps to keep up the tanks ^^ This is explained very well here.)
Holy Paladin Guear Enhancements
(Arcanums, all enhancement of guear from head to pants)
Now, as gear isn't all what you need, I'll advise you to read this very good (as always) article on Ferraro site Paladin Schmaladin (don't ask me how she got that name) How To: Healing Raids.
I have written an update of this post for patch 3.2 that changed so much about gearing in Wrath. You can read it here: Pre-raid gear in patch 3.2