Ever ran out of sandstone in the middle of a build?
Tired of grinding gunpowder for that TNT drill?
Needing a few extra redstone stacks to finish your Tic-Tac-Toe game?
Never touched obsidian but needing a blaze rod? we can't help you about that...

Well, search no further, because we have
Universal Coins!

Minecraft Wiki Thread: http://www.minecraftforum.net/topic/1833251-152forge-universal-coins-ssp-trade-items-at-will/

Description

This mod allows you to trade any items using coins. The coins come in four values: the Coin (value 1), the Coin Stack (value 9), the Large Coin Stack (value 81) and the Coin Pile (value 729). Obviously, 9 of a lower tier will get you 1 of the higher tier; also 1 of a higher tier will get you 9 of the lower tier.
The trading is done at an Universal Trade Station. The only way to get coins is by selling an item. Most vanilla items have a predefined price and prices can be changed in the config file.
Items can only be bought after the player has found at least one of that item (no buying blaze rods before finding one).

Recipes on the Minecraft Wiki.

First, you'll need a Selling Catalogue. It is only used as a crafting ingredient.

Then, craft yourself the Trading Station.

The Trade Station:

Put an item in the larger slot (top-left) and press Buy Or Sell. If you don't have enough coins to buy or if the output slots are occupied, the buttons will be grayed out.

Take the coins from the output slot and put them in the bottom-left slot to add them to the station's internal coin amount.

If the station has enough money, you can even buy the item in the top-left slot by pressing Buy.

If you ever want to retrieve the coins from the internal coin buffer, press the buttons on the bottom. The coins should appear in the bottom-right slot for you to pick up.

So please test my mod (it's the first one) and tell me what you think.