You can put them in the water you keep in your refrigerator, although I am not a fan of lemonade.
Otherwise, one can make:
– hard lemonade
– batida de limão
– lemon sorbet
– lemon ice cream
– shrimp ceviche
– Moroccan lemon chicken
– salad dressing of lemon juice and finely chopped garlic and chiles
– salad dressing of lemon juice and finely chopped cilantro and shallots
What else can one make?
Axé.
coldhearted scientist وداد 
Salted or pickled lemons sound interesting, though I have never tried them.
http://honest-food.net/2010/02/04/preserving-lemons/
I heard on the radio about preserving by packing in sugar, but I like the salting idea much better.
I know that preserving limes in chocolate, I mean packed in chocolate in two, is wonderful. I thought that bananas are the ones that taste wonderful when marinated in sugar. But you know people have different tastes and what tastes wonderful for some, others cannot appreciate it. I am all for limes in noir chocolate and sugary bananas.
No spices, I guess. But sounds hot!