Lemons and Grapefruit, what to do with them?

I have inherited a prolific producting lemon tree and a grapefruit tree.  While these trees look like they have had little attention (my sort of tree really..little attention required and but plenty of positive results.) they are now bearing so much fruit I am not sure what to do with it all.  It seems like such a waste for this fruit to fall on the ground and go to waste.  So I thought it was time to put my Edward De Bono Thinking Hat on, Green Hat is best suited, and see what the options are for me to consider on top of what I already do.

(lemon photos mine from my tree today)

1. Make marmalade.  See my previous post here about this.
2. Use a cut in half lemon in a saucer with a little water.  Turn the microwave on for about 1 minute.  Then wipe clean.  Such an easy thing to do.
3. Bake with lemons making such things as lemon mereinge pie (or the light version here), muffins, lemon cookies and lemon honey.
4. Then you can stuff the cavity of a chicken with lemon.  Bake it and hmmm beautiful
5. Squeeze lemons and freeze the juice for later use.
6. Candied Citrus Peel
7. In New Zealand a hot lemon, honey in water for sore throats.  Maybe elsewhere in the world you use this.
8. If you have a rubbish disposal system in your kitchen then a cut up lemon down this with sweeten up the disposal and maybe even clean somewhat on the inside.  I use oranges and grapefruit also for this.
9. We use lemon and baking soda on oil that has stained the garage floor.
10. Wipe the inside of my fridge down with lemon juice in warm water.  Hmmm not only is your fridge clean but is smells great too.

I am sure there are other things I can put to this list so please leave all your ideas.  I am sure that I can make good use of them.