I was wondering the same thing last year, and I found a couple of sites I'll list here for you.

Here's a few trees that aren't listed, but do well in wet areas:
Acer rubrum -- red maple
Silver Maple

Here is a link that might be useful: Trees & shrubs for wet areas

There are trees that will grow in wet soils, but do not expect them to dry it out. If anything, the shade they provide will reduce evaporation by the sun and increase wetness. Trees do eventually dry wet areas by building up the soil levels but that is a process that takes hundreds of years.

If your area is wet all year, the water table is likely high in that area. You will need to have professionaly installed drains added to the area to dry it out.

I see no need for drain tiles, and while silver maple may be good for wet areas it's not a great tree.

In zone 7 I should think there are a lot of trees that would suit your site and may or may not help dry it out.

I can think of the following as stately and nice looking trees for a wet site:

Taxodium disticum - Bald Cypress
T. ascendens - Pond Cypress
Water Tupelo (the latin escapes me, sorry)
Quercus bicolor - swamp white oak
betula nigra(?) - River birch
Or something rare (I wish would grow here!) the Glyptostrobus a Chinese relative of Taxodium and almost extinct in the wild.

Your local extension office should also have some great recommendations for both native and exotic species.

A few others that grow in the bog/wetland that is in our yard are: boxwood, and some that are listed above. Don't forget the Weeping willow, although you don't want this close too drainage pipes, wells, or foundations, as they too can cause damage

I have had a pussy willow (Salix discolor/Salix caprea) in my garden for the past 4 years and it is doing wonderfully in my wet garden. I have heard that pussy willows can get fairly large (25') very quickly, but mine is only about 10' or so tall. I planted some partial-shade and wet-feet tolerant perennials underneath and it looks fantastic!

You can find varieties that have black catkins rather than the more common silver ones. You can also get varieties that have twisted branches for seasonal interest.

If you have a friend with a pussy willow you want, just cut off a switch, dip it in rooting hormone and stick it in a mason jar with a bunch of mud in the bottom (just don't let it dry out). It'll root after a while and you can go ahead and plant it. My DH and I got our willow for $20 from a local nursery, and it was a pretty good size at the time (6'). They're not too pricey.

Good Luck!

Sweet Bay Magnolia, Swamp Oak, Tulip Poplar. I live on a wetland and they do help dry up the area around our home, but be prepared for many surface roots. With our recent floods, our trees are all surface rooting quickly.