The actual amount of cap space each NFL team has is generally a mystery. Different numbers are tossed about by any number of sources, but there's no way to truly verify whether those figures are accurate. It stands to reason, however, that the NFL Players Association would have a firm grasp on the available dollars of each potential employer for its membership. Consequently, I'd say that the numbers provided for each team in this link are as close to gospel as you'll get in the public domain.
If you don't want to click to see where your Houston Texans stand, here's a summary of the information pertinent to your favorite team:
Current Contracts: 51
Previous Year Carryover: $2,422,689.00
Team Cap: $121,663,466.00
Cap Room: $3,383,260.00