Nicole at Stitch Craft has a tutorial showing you how to sew a rolled hem with a serger.
A rolled hem is were the machine folds the fabric under a tiny bit and then stitches it. You will frequently see this around the edges of napkins and tablecloths but also on a lot of knit clothing, You may have seen rolled hems done on a standard machine but this is MUCH faster and easier!
Also, don’t miss her great post on her sewing tools of the trade. I need that point turner!
How-To: Sew a Rolled Hem with a Serger