Plenty of web sites give advice, see the RSPB web site
Bacon and other fats
You can put out fat from unsalted cuts of meat in large pieces for the birds.
Birds, such as tits, can remove morsels from them. Make sure they are well anchored to prevent large birds flying away with the whole piece! This kind of food can attract magpies and gulls, and also neighbourhood cats. If this is likely to be a problem, it's best avoided.
There is a lot of debate about the suitability of bacon rind, since much of it is salted during the curing process. As long as you can be sure the bacon is not salty, you can put it on your bird table. Since bacon can be too tough for many birds to tackle, chopping it finely will allow a wider variety of birds to eat it.
http://www.rspb.org.uk/makeahomeforwildlife/advice/helpingbirds/feeding/whatfood/scraps.aspx