I have a "wet spot" in my yard that gets very little sun. Any advice on plants that will soak up the water?
I'm not sure that plants "soak up" water to any appreciable extent. Some plants will grow in wet spots but I don't think they make the spots any less wet.
I hope someone suggests some plants for you. My experiance is mostly with trees.
I have a wet spot in my yard too. Here are the plants that have done well for many years in that spot. It's not an unusual list, but here goes. Ligularia, astilbe, chelone lyonii, solmon's seal, lobelia, ferns of course, red dock, japanese anemone. Louisiana iris does well in wet soil but I don't have any so can't recommend it personally. For grondcovers, I shop the water garden section for plants that like to live on the edge of streams.
None of these plants soak up water, so they won't dry out the spot. They're just happy living in wet soil.
I love banana trees for wet spots.
I've been thinking if more of us planted carnivorous plants, many of which are native here, we'd have a lot less mosquitos. They too won't dry out the soil but need a wet spot to do well.
http://msucares.com/lawn/landscape/types/shadelist.html has a list of shade loving plants that grow well in MS. that will get you started, as you will hav eot narrow down the water loving ones from there.