Casey - I'm doing exactly the same thing at the moment and I have found a couple of good deals.
I've been 5 times before so know roughly what i'm looking for. Do you mind NOT flying direct.
On OPODO you can fly with Nortwest Airlines and stay at 4* hotel (NYNY or Flamingo or Luxor) for a week for about �650 to �700...BUT you have to change in Minnesota.
On EXPEDIA you can get the same thing but flying with VIRGIN non-stop for about �50-60 more.
This is in September (The temp then is still about 100F during the day).
Obviously it would be cheaper if you stayed at the "poorer" end of the strip (Circus Circus, Sahara, Stratosphere) or more expensive at the Boutique hotels (Bellagio, Ceasers, Wynn).
The best value hotel I've stayed at is the Imperial Palace. Directly opposite Ceasers and half the price....good luck getting a reservation there though...they sell out quick.
Casey
We had 2 weeks last summer (May) for �749, direct from Manchester, staying 1 week in Sahara (excellent gambling), and 1 in Riviera. Fantastic experience