My hair was like that after the summer too.
First of all, get it cut!
Use leave in conditioner, and comb it through.
Vo5 miracle rescue is a good deep conditioner.
If you use a temporary dye it can smoothen your hair out.
Yes!! A trim and Aussie 3 Minute Miracle.
Aussie has done wonders for my hair - I use GHD straighteners practically every day, so u can imagine the state of my hair...well, Aussie fixes that!! (It smells like bubblegum too!)
Oh, and the Frizz-ease deep conditioning treatment is great too...
Firstly, you should get a decent shampoo suited for your hair type, not any old shampoo. K…RASTASE do a really good one Called 'Oleo Relax' for frizzy and dry hair. They do a serum which is more of an oily liquid called the same, but apply it to the ends rather than the roots to avoid making your hair greasy. Have a look here.
Before you use your hair straightners (GHD's?) make sure you use a heat protection spray of some kind to avoid damaging your hair even more. Redken have a good one which not only protects your hair from the heat, but traps the heat in, allowing your hair to keep its style for longer. Look here to find it.