(All products mentioned in this post were purchased by me; I have no affiliation with any of the brands mentioned.)
MaxCare Argan Oil Serum: This serum acts as a heat protectant; it's silicone based and contains argan oil and linseed oil. A little goes a long way, I use a dime sized amount to damp hair before I blow dry and to dry hair before I straighten or curl it (with either jumbo hot rollers or a curling wand). I find that it's most effective when I apply it first to my ends and work my way up. (I don't believe that this product is available in the States, I've only seen it here in Italy but I could be wrong.)
Suave Keratin Infusion Serum: This product contains keratin which is basically suppose to smooth and help defrizz hair; I find that it does help to both smooth and defrizz my own hair although on hot and extremely humid Mediterranean Summer days I find that it is less effective if I decide to wear my hair down. If I tie my hair up (after I heat style it) it tends to work much better, mostly likely because my body heat doesn't end up aggravating my hair and causing it to frizz.
Full Disclosure: All products in this post were purchased by me for review purposes, for any questions or concerns regarding this matter please refer to my Disclaimer/Disclosure page.