Redken Smooth Down Heat Glide Serum!
I've been through MANY a hair product and this is the only one I buy now. It's just incredible for straightened hair. For some reason it seems to bring out the colour, make it shine, smooth down everything. It's lovely stuff. Just make sure you use only one or two pumps for all your hair and smooth it through evening. If you leave it at that it doesnt leave it greasy, nice and soft
21-23 bucks, lasts me over a year and I straighten my hair every couple of days.
You can get it at Price Attack and some hairdressers.