Ice and Salt
Using a temperature probe is probably the easiest way to begin datalogging with TI-Nspire. The Vernier EasyTemp probe can be plugged directly into a TI-Nspire handheld, and this causes straightforward software to open which allows temperature and time data to be collected and displayed.
In this activity salt is added to an ice-water mixture and TI-Nspire produces a clear and interesting display of the way the temperature behaves.
There are more details about this activity in Capturing Data: Modelling and Interpretation, one of a series of booklets presenting STEM Activities with TI-Nspire, published by Texas Instruments in April 2010.