Probably more of a gimmick but they look cool. They are a little chart that is just inside a cell. It can be a line,column or win/loss. They are easy to create and could be used if you don't the all of the features and hassle of a full chart.
Here's how to create a sparkline in excel:
Start by putting you data into one column. There aren't any labels so they don't really matter for this.
Probably just a gimmick but might be useful eventually.