If you are like my mom, you may just have extra skin on your arms. (She lost 90 pounds). She works out very hard (more than I do), but the skin just never goes away. She decided to just build up big muscles - she has always been very athletic, softball/basketball player - and no, the skin isn't gone but there is big improvement.
My favorite tricep exercise is the chair dip, where you walk your feet out from your chair (or bench) and dip down, using your own body resistance. An advanced version of this would be to have your feet on another chair across from you.