As well as warming the heart (and hearth), a fire creates a raw material which can be of great value in the veggie patch.  Wood ash is a fine potash fertiliser and since it is slightly alkaline it also reduces acidity levels (similar to lime).  It contains an array of beneficial nutrients including potassium, phosphorus and magnesium which will be beneficial for fruiting crops (particularly tomatoes).  Keep your ashes dry while you are waiting to use them otherwise the nutrients will wash away.  Do not use ash from timber that has been chemically treated and never use ash from a coal fire.