Thought I should compile a list of mods I recommend for RimWorld. Unless otherwise noted, these are all compatible with version 1.3 of the game.

Vital

I consider these mods pretty non-intrusive and vital - they are all either worth starting a new save over, or can be added to existing ones.

Medical Tab

Steam Workshop

Gives you a quick overview of how your colony is doing medical-wise. Purely UI, so can be added and removed at will.

Allow Tool

Steam Workshop

Adds a bunch of tools that allows you to quickly harvest/haul/allow/forbid parts of the map. It's an essential mod to me, I use the tools all the time.

Smart Medicine

Steam Workshop

Fixes a ton of issues with doctoring in the base game (basically just "always using the same medicine type for everything" since 1.3) so you can reserve your glitterworld meds for infections and surgery.

HugsLib

Steam Workshop

Required by other mods mostly, but the ability to hit Ctrl+F12 to upload your logs and mod list is a godsend for getting help when troubleshooting.

CM Color Coded Mood Bar

Steam Workshop

Purely UI, gives you a better overview of how pawns are doing at the top of the screen.

RimHUD

Steam Workshop

Purely UI, gives you a much better panel when you select a colonist that lets you see their skills at a glance, etc.

Less Arbitrary Surgery (Continued)

Steam Workshop

Changes how surgery is calculated to be more based on skill and less reliant on RNG. Your region leading master surgeon will no longer rip off someone's arm when trying to install a wooden hand. Death is part of the game, but I'd much rather have my colonists die in a better way than a bad dice roll.

Interaction Bubbles

Steam Workshop

Purely UI, shows bubbles when pawns talk to each other. Makes things feel more alive.

Nice to have

These mods I consider nice to have, but might change too much for some people. These can still be added in the middle of a run.

Clean Pathfinding

Steam Workshop

Tosses in some small adjustments into the pathfinding algorithm to make pawns prefer paths that don't generate dirt. Saves so much sweeping.

A Dog Said... Animal Prosthetics

Steam Workshop

Adds prosthetics for animals, so you don't need to put them down the moment they lose a leg. You know you want it.

Set Up Camp

Steam Workshop

Lets your caravans, well, set up camp. Means you can set up a small temporary shack if someone gets sick on the road, has saved my colonists' lives many times.

Defensive Positions

Steam Workshop

Basically lets you preset where people should go when drafted, so you don't have to set up your colonists manually every single time a raid shows up.

Safely Hidden Away

Steam Workshop

Adds a reason to potentially settle a longer distance away from others, because it doesn't make sense that a raid party shows up every 5 days if it takes 8 days to travel.

Prisoners Should Fear Turrets

Steam Workshop

Turrets will now shoot escaping prisoners, and oppress slaves.

Prisoners Dont Have Keys

Steam Workshop

Like it says on the tin, prisoners don't have keys and need to tear down doors to make it out.

Permeable Terrain

Steam Workshop

Makes it so "liquidy" filth disappears quicker on terrain such as sand, where it otherwise doesn't rain away.

Roads of the Rim (Continued)

Steam Workshop

Lets you build roads on the world map. Takes a lot of work, but makes longer caravan trips more viable.

My Mods

Gotta plug my own stuff, I made it for a reason after all :)

Robot Vacuum (1.1 only)

GitHub or Steam Workshop

Adds a robot vacuum you can build that sweeps the place. Probably going to rework this for 1.3 some time in the future - Ideology added a bunch of stuff this can use to ease development and maintainence.

Has some fun bugs - for example you can end up being chased by manhunter vacuums.