Yes, and there is even #4 which I really want to buy.

Like Psyco said, in spite of it's confusing name, the Ultra Con lowers contrast, and the number relates to strength of the effect. Low cons are not technically a mist/diffusion filter, but they do act like one! (I've got #1 thru #3, and like I said I like em, but wouldn't use them on everything, or even most things) Ultra Cons are a more recent invention, which lift the blacks but don't have the misty effect. Ultra Cons will flare on you, though.

Now, how well do any of these do for improving DR? Maybe a little, but unless you want to start and end "milky" in the blacks (sometimes I do for a "pastel" look), I'm not sure it gives you much detail. Especially with the better patches from Driftwood or Lee Powell, you have more detail in those shadows than you might think. With a camera like the GH2, I like getting the look close in-camera. On the other hand, Shian has posted good tips on this sight for lighting to get an image that's very grade-able.

Don't the Ultra Cons produce higher contrast instead on lower? As long as I know they are used for stars and galaxies shots.

Since I use Yashica manual lens 28-105mm 2.8 with rear thread 72mm, it's a real headache to find 72mm low contrast filter.

If what you're aiming for is simply lowering the contrast for a "flatter" image, you may want to look for Ultra Cons instead, which don't have the halation around highlights and what-not a Low Con has. I like the look of Low Cons a lot, but it's a particular aesthetic that is what it is, not a short-cut to creating a flat picture style for grading. The most sterling use of Low Cons must be Kubrick - the #3 on "Barry Lyndon", and a #1 on "Eyes Wide Shut".

I have a tiffen 1/8 lo contrast filter - only used it once since getting it on sunny exteriors, but it definitely left me with shadow details to work with. Must use it more!