Mods do in fact make the WoW experience easier but most are intended to help you play, not do it for you. This guide will show you mods that will help you throughout your gameplay.

Atlas Loot enhanced
This mod shows the items (as well as drop rate) dropped off of bosses in instances and raids. I have this mod and it is very useful as to seeing what I should get to improve my gear above what I have. If you don't have this now, you should get it.

Cartographer/Mobmap (This mod will spoil gameplay)
This is a useful mod even though it has its flaws. It shows maps that you havent explored and useful for quests. It can put notes on the map and it also will let you see other members of your guild that have this on the map through a synched network. A tie in to this is mobmap. Mobmap will show npcs and coordinates. It shows profession skills and levels,merchants and their stocks, and monsters and their drop rates. (Very helpful with hard quests) This works for Outland as well.

(sorry to bring this up) Group Calendar
Need I explain?

---CT mods are very helpful, this section will cover two---
CT mail mod
For all you Auction House guru's this mod can open up all the mail inside your mailbox, it will also open checked items.
CT timer
I use to time monster respawns when I farm.

This must be the best way to make money, the only problem is bad investments you may make as a newbie auctioneer.
Auctioneer mod
It will scan the auction house for good prices on items and makes you gold with the good old saying, buy low sell high. You can seach specific sellers, items, buyout prices, and bids.

Item sync
This is one of the better mods of its type as it takes less room. It stores items that it sees on other players when you click on them and that you see on vendors and on the auction house. It can search by level and sub-type. You can also make a "favorites list" with it.

Damage meters
I will not go into this for the reason, if you don't have this... you won't care

AutoProfit
It will automatically sell all grey items in your inventory to the vendor. Useful to gamers. You can set it to the click of a button or automatically when you go to a vendor. You can make exceptions to grey items (no clue why) and exception to sell white items.

I use a lot of these and they work great.