Post any Minecraft mods you like, and would recommend.
It would be preferable for you to post a link to the Minecraft forums page, too. And a short description is also nice.
Too Many Items:Lets you spawn in any item in Minecraft, including those in other mods that you've downloaded.
http://minecraftaddon.host56.com/items-minecraft-1-2-3-in-game-inventory-editor/Aether:Opens up a new accessible area, similar to the Nether. Includes new armour, weapons and mobs.
http://www.minecraftforum.net/topic/495374-173-aether-collaboration-mod-v102-new-mobs-fixes-items-and-features/Mo' Creatures:Introduces new mobs, such as lions, tigers, bears, ogres, snakes, sharks and pandas.
http://www.minecraftforum.net/topic/81771-v125-mo-creatures-v350-with-snakes/Old Days:Makes Minecraft exactly like it was before the final version. You can toggle each feature, like fire spreading fast, old food, water ladders and trees.
http://www.minecraftforum.net/topic/534818-125-nbxlite-olddays-spawn-human-updated/Yogbox: A compilation of mods chosen by the Yogscast.
http://yogscast.com/showthread.php?11841-YogBox-A-carefully-chosen-compilation-of-good-modsSingle Player commands: Introduces commands that can be used in single player, like flying, spawning items and land editing.
http://www.minecraftforum.net/topic/94310-166-single-player-commands-v29-1-new-update/Optifine:Makes the ability to make Minecraft run smoother and with less lagg.
http://www.minecraftforum.net/topic/249637-125-optifine-hd-a2-fps-boost-hd-textures-aa-af-and-more/Equivalent Exchange:Allows the player to exchange items for better ones, for example, trading several cobblestone for coal, which can be traded for redstone, all the way up to diamonds. And new, very useful, items.
http://www.minecraftforum.net/topic/1106178-124125-equivalent-exchange-2-v1431/