Made this list for another codexer and figured this thread can always use yet another mod list. Everything (except KAS) is compatible with newest version of KSP a tthe time of posting
Big ol' list o' mods
Note: KSP only uses 32 bits, so there's a hard cap on how much RAM it'll allow. If you're crashing at start-up, odds are you have too many mods installed and it ran out of memory. You can force opengl to save a few hundred mb of mem and squeeze in a few more mods. But until the latest version of Unity 64bit plays nice with KSP, we have a hard cap on # of mods we can run
All mods: http://forum.kerbalspaceprogram.com/threads/55401-Community-Mods-and-Plugins-Library
"Mandatory"
http://forum.kerbalspaceprogram.com...e-v1-0-2c-2-9-May-15)-now-includes-Stock-Plus - Bugfixes
http://forum.kerbalspaceprogram.com/threads/55219 - Lots of mods use modmanager to check they're up to date
http://forum.kerbalspaceprogram.com/threads/60863 - Some mods still use this
http://forum.kerbalspaceprogram.com/threads/59005 - Texture compressor. Use this if KSP crashes on launch to reduce memory usage of mods
http://forum.kerbalspaceprogram.com/threads/24786 - Set up break points to stop timewarp. Remembers maneuver nodes. Critical if you're running multiple missions
http://forum.kerbalspaceprogram.com/threads/18230 - Lots of extra vessel info. Very, very handy for building since it tells you DeltaV and TWR
http://forum.kerbalspaceprogram.com/threads/47863 - A better UI for finetuning maneuver nodes
http://forum.kerbalspaceprogram.com/threads/43901 - Docking UI. Once you start doing docking for space stations or orbital assembly, you'll want this
Cool stuff
http://forum.kerbalspaceprogram.com/threads/119686 - Temperature gague to tell you if you're about to blow up
http://forum.kerbalspaceprogram.com/threads/67246 - Gives yoru kerbals medals and achiements
http://forum.kerbalspaceprogram.com/threads/60936 - Allows you to shuffle resources around. ALso (more importantly) allows you to rename kerbals!
http://forum.kerbalspaceprogram.com/threads/117471 - Super-cool working multi-function displays for IVA
http://forum.kerbalspaceprogram.com/threads/68089 - Scriptable autopilot. You can do some pretty elaborate stuff with this
http://forum.kerbalspaceprogram.com/threads/16925 - Pretty lights for your ships
Graphixwhoring
http://forum.kerbalspaceprogram.com/threads/101496 - Fancy new collision effects :D
http://forum.kerbalspaceprogram.com/threads/98943 - Creates little dots (and optionally labels them) that show really distant objects, including your own ships
http://forum.kerbalspaceprogram.com/threads/55905 - Configurable admosphere, clouds, lights on night side of kerbin. Needed for other upgrade packs such as Astronomer's
http://forum.kerbalspaceprogram.com/threads/115408 - Alternative to Environmental Visual Enhancements (no clouds though). Adds atmospheric scattering to make flying at planets look prettier.
http://forum.kerbalspaceprogram.com/threads/65754 - New particle effects for engines
http://forum.kerbalspaceprogram.com/threads/96497 - Makes planets reflect light back onto vessels that orbit it. Subtle, but very nice
http://forum.kerbalspaceprogram.com/threads/107471 - Allows you to replace in-game textures (check textuer packs in thread). Custom skyboxes are nice. Needed for things like Renaissance Compilation
More difficulty
http://forum.kerbalspaceprogram.com/threads/83305 - Signal bouncer. Build your own satellite network or lose control of your unmanned probes! :D
http://forum.kerbalspaceprogram.com/threads/106580 - Extra contracts for Remotetech
http://forum.kerbalspaceprogram.com/threads/40667 - Life support
http://forum.kerbalspaceprogram.com/threads/64972 - Cooler-looking modules for life support (also supports dmagic orbital science)
More stuff to do
http://forum.kerbalspaceprogram.com/threads/80369 - Altimetry/biome scanner. Make your own mapping satellites. Integrates with rasterpropmonitor
http://forum.kerbalspaceprogram.com/threads/64972 - New types of science experiments
http://forum.kerbalspaceprogram.com/threads/79588 - Build colonies on other planets. Supports TAC life support
http://forum.kerbalspaceprogram.com/threads/92514 [NOT UPDATED FOR 1.0 YET] Amazing mod that lets kerbals pick up and attach things to each other. Assemble stuff on ground. Drag fuel pipes between rockets without docking etc.
http://forum.kerbalspaceprogram.com/threads/113111 - Inventory panel. Similar to (and compatible with, once upgraded) KAS
http://forum.kerbalspaceprogram.com/threads/116064 - Adds controllable joints, rotators and the like for building your own mechs. (Also useful for making payloads that fold up to fit inside a fairing)