This can be a hard question to answer. Everyone has their own particular brand of bikes that they like, and many times the "suggested" beginner bikes can start at $1000+. If it's sturdy and put together well, and "box store" bike can be just as useful as an expensive one. I do fine riding the mountains every weekend with my $250 S-60 Schwinn FS bought at Target, My buddies I ride with have much more expensive bikes then me, and I keep up with them.

That being said, I recently just bought a 2006 DBR Podium 1 road bike for way less then retail that was put together badly by the Navy Exchange (I'm in the military). After taking it immediately in to my local shop for a tune-up, I still spent less on that bike than a comparable one at the shop.

Now, on to my recommendations, you can get a new 2007 Podium 1 for about $600-650 or a Podium 2 for about $800 at a store such as Sport Chalet or Sports Authority. Steer clear of stores such as Target, Wal-mart, etc for road bikes as they tend to have way-off brands or crappy 14-speed Schwinns. Some bike shops will have low end bikes for sell starting in the $500s, but they'll often try to pressure you into something more then what you really need. It's amazing how many people I see buying $1500 FS mountain bikes when I go through a bike shop, knowing most of them will never see a dirt trail.

Anyway, good luck riding from a guy who hits the trails every weekend and roads it to work through the week.