Forget about a big name frame. I own several Treks and I am telling you this so that you can get the most bang for you buck.
Put your money into the bike that can give you the nicest components (shifters, derailleurs, cranks, bottom bracket, brakes, wheels, etc)
Nicer components will make for a much more enjoyable experience than a fancy frame.
Make sure you get a frame that fits.
Make sure you get a bike that fits what you see yourself doing on your bike. Do not get a road bike or a mountain bike if you aren't going to do a lot of miles on the road or ride lots of single track trails.
If what you want to do is cruise around your neighborhood, then get a townie style bike.
Trust me, bicycles are a HUGE part of my life.
I have at least 5 grand in just my Mt. bike and I am hear tell you that 300 bucks can get you a very nice beginers ride.