If you're just getting into the world of Minecraft mods, here are ten of the most popular ones that are a great place to start. If you need help understanding what mods are all about, you also might want to check out the article What Are Minecraft Mods.
Important Safety Tip! As with any file downloaded from the internet, there is a chance that mods may contain viruses or malware. Always be extremely careful when downloading any mod file. Before you start, read through the Safety Tips For Downloading Mods and How To Spot Fake Or Misleading Download Links for more info about how to download safely.
Adds over 40 creatures like werewolves and mammoths, as well as the ability to tame and ride some of them. Very cool.
A bunch of really useful mods that do things like allow you to stack unstackable stuff (doors, boats), create a chest that keeps your inventory safe when you die, make display shelves and a book of all the recipes. There are also mods that do fun things like make creepers rain arrows instead of exploding.
A super popular mod that makes villagers more interesting - they have lots of different skins, and you can even marry them and start a family.
A handy way to see what's around you - creatures, caves, resources. You'll never get lost with this mod.
A mod for making the game look better - higher definition textures, better frame rates, less lag, customized lighting and colours. The water looks fantastic with this mod, and you can see better underwater too.
These two similar mods make managing your inventory easier, as well as letting you craft, brew and enchant items quickly. Not Enough Items also includes recipes.
For making epic explosions.
For crafting a backpack that you can use to take items along with you as you explore.
Instantly make houses, pools, fountains, stables and other structures.
Train your dog to play fetch, protect you, go fishing and other talents.
That should be plenty to get you started! Don't forget to check out The Parent's Guide To Installing Minecraft Mods if you need help figuring out what to do. And if you're looking for more mods to try, check out Another List Of Cool Minecraft Mods.