Well what type of riding are you going to do? Just the casual around the neighborhood cycling? Or something a bit more competitive? There's pretty much a bike out there that will suit your needs, depending on price point and features. Just to give you some ideas, here are some different bikes and what they're best for. I'm using the Giant brand models because that's what my shop keeps as their stock models, but pretty much every bike company will have similar lines at comparable pricepoints. Honestly, while you'll get people swearing by this that or the other brand, for the most part it's a matter of personal preference and most of the major established bicycle brands (Giant, Schwinn, Mongoose, Trek, ect) will offer pretty much the same standards. Most will offer lifetime warranties on frames, ect.
This category is kind of ill defined and the definition will change depending on who you ask. But here are the two bikes I would generally consider a "hybrid"
This is more of a mountain style hybrid. Wider tires, larger tread, front shock,disc brakes, the smaller 26" wheels, but still, not something you would want to do serious off roading in. This is much more a "muddy dirt path" sort of bike. Great for casual riding around the neighborhood or on some more dirty/rocky trails.
This one's more of a road hybrid. The larger wheels (700c), less tread, ect. This one is the neighborhood cruiser, or nicely paved bike path. It's still got the shock for comfort, and I'm sure some models have disc brakes (not that they're all that necessary), but still a good neighborhood bike.
Both of those bikes will have you sitting a lot more upright and are designed more for comfort. They can of course be adjusted to something more aggressive or more upright depending on preference, but those will be the standard models you find that are for casual, comfortable biking. Price ranges for these bikes are about $300-$400.
Another option in a more hybrid-ish category is something like this:
This is a road bike, but missing the downswept handlebars, and there are still normal pedals. This will run about $500-$700.
There are also the options of full out road or mountain bikes:
These will each run about $1000, and I'd say for an entry level model into either genre of biking that's a reasonable amount to pay. The technical aspect of each of course vary, but the bottom line of each is the road bike is very tailored to speed and roads, whereas the mountain bike with the full suspension is very adapted for uneven surfaces.
So those are the different types of bikes, but as far as which model/brand/type you want, it's really up to you. As I said, your established bicycle brands of comparable quality and value. Don't let yourself be talked into one kind of bike or the other. If I were to make a recommendation for you right now, since you're looking to get back into cycling and your profile says you are looking to get back in shape, I'd probably suggest the third bike, the road bike without the downswept handlebar. It'll still offer you a bit more comfort and upright-ness for casual riding, but also provides more of a performance edge for some more active and exercise centric riding. But again, I don't know much about you or your fitness goals, so I'm kinda making some assumptions and guessing. What are your end fitness goals? If you potentially want cycling to be a part of your fitness routine (and watch out, it's very addicting
), then hell, get yourself a road bike.
So the moral of the story is: There are a number of different types to choose from, but in the end choose one that lines up the most closely with what you want to use your bike for!