I started testing some of these addons and they appear to be functional for the 1.12.1 client. I haven't tested nearly all of them nor do I intend to, there is literally hundreds of them. They are sorted in alphabetical folders.
Download the rar file here:
http://www.mediafire.com/?7zaf00k1g5667y1
And then you can use this website to search the addon folder names to figure out what they do, if it's not self-explanatory. Most have some sort of readme in their folder to explain functions though:
http://wow.curse.com/search/SearchResults.aspx?q=
You guys should help go through this archive and pick out the best addons then post your findings for the rest of us. It would be really helpful to know which ones are the best without having to go through all of them ourselves.
The ones I am trying out so far are:
Atlas (shows dungeon and battleground maps)
AtlasLoot (lists bosses and loot dropped in those maps)
AtlasQuest (lists quests for both horde and alliance for dungeons)
AutoProfit (automatically sells grey junk items to vendors for you)
BigWigs (basically the original Boss Mods afaik. Scripts raid fights to help give warnings about the fight as it progresses)
BuffWatch (can keep track of buffs on yourself / group / raid. Has single-click rebuffing functionality when buffs fade)
PVPLog (keeps logs and statistics of the people you have PVP'd against in duels, BG's, etc. When you mouse over them it will show your wins/losses against them, you can also search player names to bring up those stats. Can also auto-report kills and deaths to guild and world chat)
SCT (scrolling combat text - adds buffs, debuffs, heals, damage vs. and damage against as scrolling text that can be completely customized)