OK so this isn't very Christmasy but it's very bargainous!
I've just been shocked by the savings to be made on changing some light bulbs to LED ones, particularly now that they're coming down quite considerably in price. I noticed Costco had got a load of new ones in, all sorts of different ones which is what prompted me to have a look.
I have a very dark kitchen so have the lights on a lot, plus we tend to leave the landing lights on during the night and the hall lights on during the evening. These three places have 16 bulbs between them - and using the calculator below I reckon switching would save me about £250 in electricity costs in the first year. I would need to buy bulbs in that first year which seems to be £2-5/bulb - but even getting the £5 bulbs I would be quids in.
I was originally thinking I would switch over as old bulbs failed but having done the sums, I'm just going to do the ones that get used a lot straight away.
Have a play with the calculator here - for reference, I discovered I have the 'energy saving' 70 watt halogen bulbs in my kitchen and the halogen 50 watt bulbs in my hall/landing. We've put in one LED light in the kitchen to try and it's as bright if not brighter than the rest, plus it is bright immediately rather than needing to warm up like the older energy saving ones.
Hoping that these simple switches will go a long way towards paying for next Christmas 
sorry it's not a very present-y bargain post though!