What entry level DSLR do you recommend?

$600 is a good chunk of change. I've seen Mamiya digital systems for a little more than that. If your serious about photography, then I advise to go Medium Format. Otherwise, the LUMIX DCM-G2K would be my advise. Panasonic electronics with Leica optics. Nikon has their good gear, but mixed with low consumer fecal matter --- read the reviews.

The next move forward is BIGGER (ie. Digital Medium/Large Format Cameras)

Bigger is Better: Similar to film formats, larger sensors offer higher resolution, greater dynamic range, more color depth and bigger pixels as compared to smaller sensors

Film Format Digital Format

I do recommend the Nikon D3000 and the Sony alpha series. The Pentax KX was nice, too.

I like the Cannon Rebel T2i. I think Cannon makes the best cameras, and this is no exception. This records video very well too, so that is kind of a bonus.

I'd recommend the Nikon D5000 or Canon Rebel T2i. Both shoot video, but Canon performs better. The Canon may up the price, but believe me, you get what you pay for. In terms of photo, either one would work.

I would not recommend the D3000, it got pretty bad reviews, however, it's replacement, the D3100 is a great camera. It has the added advantage of a video option, should you decide to try that out some time in the future too. The official price is a bit out of your recommended range, at $700, but you can get it on Amazon (and likely other places too) for less than $600.

I'm not sure where the first responder thinks he can get a Mamiya Digital Medium Format for little more than "$600" that is really a pretty low end dslr at that point. Mamiya's 645DF is a great camera but sticker price is $5995!

Pentax is often overlooked but make great cameras and if you have a Pentax film slr you can use your existing lenses on your Pentax dslr. That can sometimes be true with certain Nikon and Canon lenses on their respective bodies but isn't as clear an answer as with Pentax.

Beyond that what is the intended usage? If you have any desire to use an accessory flash, or flash triggers to use with off camera or studio flash then I would avoid Sony as they require an "adapter" to work with a normal trigger such as a Pocket Wizard.

If you are starting from scratch for both a body and lenses Canon will probably give the best bang for the buck and the T2i is a fantastic camera. Nikon's bodies tend to be a little cheaper than equivalent Canon's but Canon's lenses and other accessories tend to be a little cheaper and if you compare the Nikon + a flash + 3 lenses against the same from Canon, you'll likely save money.

Another consideration is if you plan on shooting anything with moving objects such as your kids sports. The autofocus system in the Canon T2i (or an even better camera the 7d) is pretty phenomenal.

If your only interest is basic snapshots and vacation photos, you'll truly be happy with most any dslr on the market. If you want to expand and have a camera with a large network of users to learn from stick with the Nikon or Canon's and then go try them both out at a store before deciding. I chose a Canon (7d) because of the AF speed and it just felt better in my hand. Some people like the Nikons for that same reason, especially if their hands are a tad on the smaller side.