Oh, Christmas tree, oh, Christmas tree! How lovely are thy branches!

And needles, resin, cones, bark...

The evergreens we bring into our homes and landscapes need not be merely ornamental. They're a great boon to the ol' homestead, in many ways, and have the potential to outdo most other trees, in their practical contributions. Even left alone, they make incredible mini-ecosystems, all by themselves. But.....

The needles can be left to fall from the tree and dry, then raked up and used as mulch, fire starters, or added to compost or potpourri. Or, collect them when they're freshly fallen, to make a very relaxing, soothing tea that's high in vitamin C - or weave into baskets, placemats, coasters, trivets, etc.

The branches can be the base on which to build emergency shelter for you - or your critters, make quite effective brooms, can be bent into effective emergency snowshoes, stripped of the needles, and wooden into larger, sturdier baskets, and more.

The bark can be used as a firestarter, a splint, made into small trugs, used as roofing singles for temporary shelters, and more.

The pinecones make even better firestarters, plus bird feeders, or air fresheners, and they provide pine nuts, and their arts & crafts potential is limited only by the imagination of the crafter.

The sap is a fantastic addition to your first aid kit - for sealing wounds, or simmering for a steam, to open the sinuses (add some needles, for an extra boost!). It can also be used as the fragrant binding material, to make incense. The sap is very sticky and difficult to remove, so can be used as an adhesive, or for sealing bowls and such, or as an addition to soap, for a clean, fresh smelling, antibacterial boost.

Different varieties have different additional benefits. For example, juniper, while its viciously spiked little needles are painful on the skin, also offer the Juniper berries that give gin is distinctive flavor, and are sometimes used in the culinary arts. Rosemary, with its woody stems, and famous culinary uses, is also a medicinal evergreen.

They make great living privacy screens, and those prickly junipers make a darn good security shrub or tree, around windows, to discourage cat burglars and peeping toms. Goats love to eat many evergreens - but, in my experience, not so much, with juniper.
This list only scratches the surface. What ways do you use them?

Wow, you really covered the topic! One more I can think of, offhand, is pollen. I haven't collected pine pollen yet but I understand it is supposed to be antioxidant, anti-aging, high in fiber, etc. I am thinking it would be smart to plant some low growing pines like mugo (mugho?) to keep the pollen spikes within reach for harvesting.

Essential oils can be distilled out of many conifers. You can get that effect by bringing boughs or trees into the house. I find it clears the mind, and the steam from simmering conifers in water is good for clearing the sinuses.

I remember in Cape Cod, the town used to collect the used christmas trees and pile them along the upper edges of beaches to catch sand and reduce erosion. I don't know if they still do that

As with many mature trees, older spruce have an abundance of dead limbs near the base of the tree.....but with very dry twigs still attached.  These outperform any other kindling on the property for starting the woodstove, igniting quickly, yet providing a long enough burn time to get the larger elm pieces burning.

We love to put our used tree into our winter chicken coop as cover and a "toy" and to have the needles enrich the chicken duff which we then compost. But here's a whole 'nother idea below: replanting it! https://www.cbc.ca/news/technology/what-on-earth-christmas-tree-live-1.5836182

We always put ours out near the bird feeders after Christmas as a quick and safe haven for the birds. After it turns brown, we chip it up for mulch.

Here's a podcast from Joe Lamp'l, a.k.a. Joe Gardener, I just listened to today about Why Real Christmas Trees are better for the Environment than Artificial

Here ya go, for some more great info on pines, specifically: https://www.healingharvesthomestead.com/home/2020/12/23/foraging-identifying-harvesting-and-using-pine-needles-for-your-wellness

Unsold live 'christmas trees' can be had at a very reduced price- after the holidays.
Some places get in sheered rosemary 'cones' that can be reverse engineered back to a more natural state over time.
I doubt it would be wise to use these for herbal/edible uses until the fertilizers (and what all) are flushed from the plants system.

   We were fortunate to pick up 3, 5 gallon Italian Stone pines a few years ago.
   Currently established well in a hugal pile and we're looking forward to homegrown authentic pine nuts, eventually...None to date.
       Continuing to substitute lack of pinenuts with sunflower seeds or walnuts while we wait.
   Pinecones can be used for a plethora of craft projects. The rabbit enjoy them as chewable toys.
        Neighborhood foraging of fallen pine cones is an option.
        Accumulate a stash of pinecones for adding to wreaths, bird feeders, sliced into segments and painted like flowers with recycled paint.
           Upcycling for gifts, barter, or even possible income

Pre-shop /preplan before the holiday to see what is available and what might work for your plot and projects.
Cell phone is a great tool to research varieties available on the fly as to practicality to actually grow where you need a conifer to grow.
Be mindful of water requirements, sun exposure, original/native range and adaptability.
What could you grow as an understory guild with pine trees?