Download:
http://db.tt/b4MatAN5TooManyItems is an inventory mod that allows you to create items in both single- and multi-player. When you open your inventory screen, left-click on the items on the right to add a full stack, or right-click to add 1 at a time. It has more features also, like fast crafting, moving items quickly to the chest, and a trash icon. You can also "save" your inventory for later, meaning you can transfer that loadout between worlds. With this mod you can also control the weather and the time of day.
Enjoy!
How to install mods:
http://tinyurl.com/howtoinstallmods