ItemRenderer
renderItem(EntityLivingBase, ItemStack, int) Renders the item stack for being in an entity's hand Args: itemStack
renderItem(EntityLivingBase, ItemStack, int, ItemRenderType) Renders the item stack for being in an entity's hand Args: itemStack
renderItemIn2D(Tessellator, float, float, float, float, int, int, float) Renders an item held in hand as a 2D texture with thickness
renderItemInFirstPerson(float) Renders the active item in the player's hand when in first person mode. Args: partialTickTime
and so on...

RenderItem
doRender(EntityItem, double, double, double, float, float) needs EntityItem
renderItemIntoGUI(FontRenderer, TextureManager, ItemStack, int, int, boolean) Yes here is a method for rendering itemstack
some more methods