If you want to really add some flair to your New Year's Eve cocktail and wine glasses, this DIY tutorial will help you make simple LED wine-charms for your glasses.
Over at the DIY tutorial site Instructables user BillR has put together a guide to turning an LED and a battery into a light-up charm for your glasses. The design requires a tiny bit of soldering but it's about as simple as any electronics project could be and technically, if you had LEDs with long enough wire leads, you could skip the soldering all together.
If you wanted to be extra crafty you could find some way to temporarily affix the LED to the stem, directed upwards — a band of black electrical tape perhaps? — so that the light diffuses through the stem, glass, and liquid inside. If you like the idea of having a colourful way to mark glasses but don't want to bust out the soldering iron to do so, use window markers instead. Have a clever way to help people identify their glasses?