Now a Category 2 hurricane with sustained winds of 100mph+, Rita is glancing the Florida Keys as I type.

Consistent with Bryan's earlier prediction (Key West radar clearly shows the Hurricane Rita has formed an eye, although Dvorak satellite shots are still missing this feature. This could be setting the stage for explosive growth soon. 1038AM EDT) Katrina has rapidly strengthened with a 2pm advisory putting Rita at 978mb; a drop of 13mb over the past 12 hours. While we have seen some explosive pressure drops this year, a consistent drop of 1mb+ per hour is a quickly strengthening storm.
Looking at the graphic above, NHC is forecasting continuted strengthening from Rita which isn't surprising given the current state of the Gulf of Mexico. As requested, here are the current Sea Surface Temperatures (SST) for the region:

As you can see, the entire Gulf is between 28 and 30 degrees celsius, which is certainly warm enough to feed the hurricane.
This image shows 'total cyclone heat potential'; basically how much 'hurricane fuel' there is in the Gulf of Mexico, for lack of a better term.

There is certainly plenty of nice water for Rita to strengthen further, and in fact, Rita's projected path pretty much goes across the best area for strengthening.
The next advisory comes out at 5pm EDT, but the latest data from Hurricane Hunter aircraft shows a drop in pressure to 976mb, continuing the ~1mb drop/hr trend.