Bronze

Bronze is an alloy added and used by Forestry, IndustrialCraft 2, GregTech and Thermal Expansion. Tinkers' Construct also adds it, but it is called Tinker's Alloy.

Forestry
Bronze Ingots can be made in Forestry by combining 3 Copper Ingots and 1 Tin Ingot in a Crafting Table:

IndustrialCraft 2
Bronze Dust can be made in IndustrialCraft 2 by combining 3 Copper and 1 Tin Dust, Crushed or Purified Crushed Ore. Ingots can be acquired by smelting the dust. Bronze Dust can also be made by Crafting or Compressing 9 Tile Piles of Bronze Dusts:

Tiny Piles of Bronze Dust can be made from macerating a Bronze Plate:

GregTech
Bronze dust can be created by combining 3 Copper dust and 1 Tin dust in the Crafting Table. This recipe is considered inefficient due to the ratio of materials:output being 4:3, which is 25% loss of materials.

Using a Mixer to combine the dusts is more efficient.

Bronze can also be created by combining ingots and/or dust in the Alloy Smelter. This recipe is considered more efficient than the shapeless crafting recipe, because it has a 1:1 input:output ratio, providing no loss of materials.

The Copper can be replaced with Tetrahedrite although this is less efficient.