inexpensive all-purpose bike?

Go to all the LBS's in your area and try a few bikes and see what feels best for you. They all are durable fun bikes. I just got on a Trek 7.3fx for 610. at my LBS. First 100 miles and I'm very happy. Seats a little firm, but other than that, its a good bike. Like I said, there are many good choices. My money would go to Trek, Cannondale, Specialized. I would stay with an LBS vs a brick and mortar outlet. Better service.
Why I chose the 7.3 was for riding position for me, tires, wheels and component choice was good for the money I paid. I would have gotten a 7.4 if there was one on the floor without ordering one. It has a carbon fork vs aluminum. Not that big a deal.

It's great to support your local LBS, I guess, but if you are really trying to save money, there are a couple of things you should know -
1. The bike brand name is just about meaningless, in the "inexpensive" category.
That doesn't mean you can buy a Walmart or Target bike and be happy - stay away from all the bigbox brands because there is a tremendous difference between those bikes and "decent" bikes. My wife's first bike was from Walmart and she "didn't like" biking until I bought here a decent bike. I tried her Walmart bike myself and it was nearly twice as hard to pedal as my Fuji mountain bike! But there are only a few companies that make frames for what I'll call "real" bikes, so what brand name gets stamped onto them doesn't mean a lot.
2. You can get a good road, hybrid or mountain bike online from bikesdirect.com for $300 and up. My $300 Mercier Galaxie roadie compares with a friend's $800 LBS road bike. They both ride identically and have pretty much the same components.
3. Don't get sold on needing a special frame material (i.e.: carbon, aluminum, or kryptonite). Nowadays, steel frames (alloyed with other materials) can be as light as any other type, and steel generally lasts longer, is more repairable and is more forgiving of rough use. I have a mix of aluminum and steel frames (6 bikes) and you can't tell them apart by the ride - you have to read the fine print on the frame to even know what they're made of.
4. Do read up on how to properly size a bike and be sure to get one that fits you properly.
5. Do not think that by buying from an LBS you won't have to learn how to do basic maintenance and tuning on your bike. The bikes we bought from LBS's didn't get the service that was promised on one case, and things were incompetently done in the other case. If you ride a lot, you're going to want to do these things yourself anyway, so may as well dive right in!
Good luck and welcome to biking!