Frontier has reduced fares to/from Houston IAH. But this isn't one of those skimpy-date sales: it's good for travel through March 9, 2008. Not every day of the year will be available on every route, but technically the sale is valid for travel 7 days a week (in reality, a lot of peak travel days--Fri, Mon, etc) are sold out many months of the year. And like all rock bottom sales, don't expect to be able to travel over peak holidays.
Fares are $178 RT plus tax, mostly between Houston and airports in the West, Southwest, Northwest and Midwest. Examples include Houston to San Jose CA, Spokane, Reno, Seattle, and Boise.
We've listed these deals on our Houston fares page.