Download Gearscore, Deadly Boss, Healbot, Recount 4.0.6 Addons @Curse.com
Tomorrow the patch will get applied, the realms will be down from 3 AM to 11 PM, if there won’t be an extended maintenance.
Deadly Boss: http://wow.curse.com/downloads/wow-addons/details/deadly-boss-mods.aspx (26 January update)
Recount: http://wow.curse.com/downloads/wow-addons/details/recount.aspx (31 December 2010 update)
Healbot: http://wow.curse.com/downloads/wow-addons/details/heal-bot-continued.aspx (30 January update)
These are the most downloaded addons from curse.com
Usually the new updates are going to get uploaded on the same pages as you see here. Most of the addons will still work on 4.0.6 even tough they are officially designed for 4.0.3 (current patch).
Another popular addon these days seems to be Npc scan (http://wow.curse.com/downloads/wow-addons/details/npcscan.aspx).
It will tell you a record of rare mobs, useful for hunter (taming rare pets), but also there are rare mounts, and mobs that will give achievements.
http://prettypls.com/general/patch-4-0-6-changes-update-january-12 are the pages with the 4.0.6 changes, for an exact list of changes visit us.battle.net, and check the latest entry on their blog.