I work for a large corporation and am on a set salary. I normally work 5 days a week, but sometimes am scheduled 6 or 7. My question is this:

If I work more than normal in a given week, but only receive my normal weekly salary, shouldn't I also receive my normal salary if I should happen to work less than normal in a particular week? This happened to me 2 weeks ago. I was only able to work 4 days due to an illness, and my employer only paid me for 4 days of salary instead of my usual 5. Next week, I am scheduled for 6 days, but I am not going to receive anything extra. This seems to be one sided in favor of the employer.

Any thoughts?

Assuming you are an exempt employee ("salaried" is merely a pay method), there are only certain situations in which an exempt employee's salary can legally be docked. See specifically, paragraph (a)(3).
http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_541/29CFR541.118.htm

If your employer has docked your salary (although it is perfectly legal for the employer to substitute your paid leave time, such as vacation, for your regular salary) in violation of the FLSA, you can file a claim for unpaid wages with the Texas Workforce Commission.