Does anybody know of good products out there that eliminate curls in straight hair? I use shampoo and conditioner and designed to keep hair straight, but the next day it starts to curl up. The only thing I can think of doing it straighting it the next day and putting hair spray on it, but that'd get tiring.

Assuming you don't have tight curls, just waves, you might try using a leave-in conditioner or using some light oil like jojoba oil on the length of your hair.  The extra weight will help keep the waves to a mininimum.

As your hair gets longer you will find that either the weight of your hair makes it straighter or or waves will become more defined and you will actually start to appreciate them (I know I did!).

They're not really waves, but I don't think they're tight curls either. Although I've noticed as my hair gets longer it doesn't curl up as fast, and it's fine for the most part, as long as I wash it as often as I do.

I wouldn't mind if it was wavy, it just doesn't seem to do that. I also think part of it is humidity on hot days, it's a lot hotter this year than it was this time of year last year where I live