Here are the mods I recommend. These are all compatible with the latest versions of SMAPI and Stardew Valley on Linux/Mac/Windows. See the player's guide to using mods if you're interested.
Quality of life
I think the best mods are those which improve the game while maintaining its balance, lore, and style.
Customise the sprinkler radius, with a proportional change to their cost. If you're willing to mine all the ores you'll need, that makes the basic sprinklers useful early in the game and lets you do more than just watering crops every day.
View the calendar anywhere. See upcoming birthdays and festivals without needing to walk to the nearest calendar.
Access, label, and categorise your chests from anywhere (with optional balanced mode). Makes inventory management less of a chore — you can have multiple organised chests and sort things away without walking around trying to find which chest is which.
Children Like Parents
Your children will look a bit like your spouse (instead of the default generic children).
Daily Quest Anywhere
See the quest board anywhere, so you can check for a daily quest without walking all the way to Pierre's shop.
Toggle an overlay to see live bee house / Junimo hut / scarecrow / sprinkler coverage, hidden paths and warp points, and more. Very useful when laying out your crops.
Makes the routine player animations (breaking geodes, eating, drinking, etc) almost instant.
You'll often find you left your horse across town, or the horse can't pass through a narrow path. This mod eliminates horse location management as a game mechanic; just whistle and he'll
come runningteleport to you.
Point at almost anything, and press a button to see information about it. This helps you decide whether an item is worth keeping (e.g. it shows what bundles/recipes/achievements you still need it for), plan your crops (e.g. it tells you when a crop will be ready), manage trees (e.g. it tells you whether something is blocking their growth), see what gifts an NPC likes, etc.
⚠ Looking up items or NPCs shows all gift tastes. Look up things responsibly if you want to avoid spoilers.
Point at a farm animal and it'll show whether you've pet them today, without needing to check them manually.
No Soil Decay Redux
Ensures that plots you till stay tilled. This lets you till the area you'll be planting ahead of time to plan your crop layout, without worrying that your neat layout will decay.
NPC Map Locations
NPCs move around a lot, and it can be frustrating to find them when you need to talk to them. This mod shows their locations on your map.
Pony Weight Loss Program
Lets the horse pass anywhere you can. This eliminates a common annoyance where the horse can't pass through narrow paths.
Stone Bridge over Pond
Adds a bridge across the pond at the bottom of the standard farm, so you can have a straight path between the top and bottom exits.
While Clint is upgrading one of your tools, he'll let you rent an old one he has until yours is ready.
When you enter a shop and the shopkeeper isn't behind the counter, you can still buy from them.
Skips the starting splash screens and (optionally) the title screen. It's only a few seconds each time, but you won't be able to go back once you're used to this mod.
Lets you plant crops (and grass) on the grassy portions of the farm map.
Tool Upgrade Delivery Service
After you ask Clint to upgrade a tool, he'll send it back in the mail when it's done. (You can still go pick it up yourself if you want.)
These mods are best used later in the game, once you've already played for a while with the vanilla mechanics.
When you're tired of manually working each machine, this opens a whole new gameplay mechanic. Place a chest next to a machine (like a furnace or crystalarium), and the machine will pull raw items from the chest and push processed items into it. Connect multiple machines with a chest to create factories.
Adds an explorable, procedurally-generated forest area to the game with many secrets and resources.
Instantly access all of the game shops through their website at the press of a button.
Buy a tractor from Robin to make managing large farms much easier. The tractor lets you quickly clear debris, plant/fertilise/water/harvest crops, etc.
These mods visually tweak the game using Content Patcher.
Fixed Mouse House
Give the hat mouse a less broken-down house.
Change the Gold Clock to fit in better the game style and look a bit less ostentatious.
Rustic Traveling Cart
Change the traveling cart to better fit the game style and look a bit less silly.
For mod testing
These mods are useful for mod developers.
CJB Cheats Menu
Adds many useful utilities like teleporting, changing the time, building instantly, making machines finish instantly, etc.
CJB Item Spawner
Lets you instantly spawn any item in the game.
Press a button to show debug info like the tile coordinate under the cursor, and enable the game's debug features like teleporting.
Fast travel to any named location on the map by clicking it. Immensely useful when testing to avoid needing to walk everywhere.
config.json, point at almost anything in the game, and press
F1to see all the hidden data about it.