As far as trees are concerned, if you are thinking about bringing one down or want shade you need to plant a tree now. They take a while to establish, like a few years before they'll really start growing well.
When I was looking for trees I searched and searched online and found a lot of good articles from the USU extension.
This is a good article to check out and may give some ideas on where to look. I've planted a bunch of trees and replaced a few that didn't work out. Currently I have 3 bur oaks, 1 red oak, 1 columnar oak, 1 linden, 1 kentucky coffee tree which are all expected to grow tall and provide shade down the road. I also have some ornamental trees that are more for looking pretty than for shade, they are...1 spring snow crab apple, 1 coralburst crab apple, 1 prairiefire crab apple, and 5 flowering pear trees. All the crab apples are doing great and are staying long term. The flowering pears are kind of garbage but I bought them for almost nothing a few years ago. I'll likely pull these out in the next while and replace them with something that will look good and provide better shade long term. I did have some sycamore trees that didn't make it, in my opinion due to their size in the pot I got them in, and I didn't untangle their roots. I've also managed to kill a magnolia as well.
I would never plant an aspen or cottonwood. I grew up with aspens at my home and had the same experience Bart did, I hate them as yard trees. I do miss the sound the leaves make when the wind blows through them but not enough to plant those damn trees. My parents have also had really good luck with honeylocust trees both at their old house in kearns and their new one in west jordan. These are nice because they grow pretty quick and the leaves are real small so you don't have to rake, they mulch with the mower really well.
One last thing on trees. I prefer to buy and plant smaller trees than to pay buckets of money for big trees. The smaller trees cost less, are easier to manage, and hurt less if they die. The big trees in the small buckets are missing a ton of roots and take a long time to get back established where the smaller ones seem to bounce back quicker in my opinion. Regardless, its going to take years to get real growth anyway.