Depends on what you want, the M&P 15 is a good gun at a good price, IMO the 15T is one of the best OOB AR's for the price. 
You can also look at Spikes tactical. They have a very good AR 15 for around $700-$800 no frills but rock solid and ready to shoot. This is probably the best rifle you can get for under $800, and is comparable to more expensive AR's ( Stag, S&W, RRA ). Also by far the best barrel, and bolt carrier group you can get in a complete rifle for less than $1000.
You can get a Bushmaster or DPMS for the $900-$1000 range but IMO they are not as dependable as the S&W, RRA, or Spikes. 
Rock Rivers are a little more expensive and might push your budget, especialy if you want the extras. RRA is a little better quality as the M&P 15T.
You also might be able to find a deal on a used Larue or Noveske, but these will push your budget, a new one will run from about $1600- $2400, depending on features. Excellent AR's and worth every penny just pricey. Besides that Larue's are made in Texas. 
 
 
If in doubt buy a stripped lower and build your own, you can make it the way you want it, and save some money too. I just got a stripped M&P 15 lower for $135. Besides that its fun.  
