Switch

Recommended systems: all old units. 4.1.0 or 7.0.1 (latter currently unreleased) for all units.

Use https://ismyswitchpatched.com to find out if your unit is older or newer. The RCM hardware exploit works on all system versions, but it only exists in older models.
Regardless of the unit you have, if you are on system version 7.0.1 or lower, you can use warmboot.
If you update normally you will burn your eFuses and you won't be able to downgrade, read below to know more. This is relevant to everyone, including owners of old units, because downgrading can give you access to more software exploits (such as warmboot on 7.0.1).

USEFUL LINKS
[start here] Switch hacking guide: https://nh-server.github.io/switch-guide

Frequently Asked Questions: https://pastebin.com/CAMZ2eVr
Helpful links: https://pastebin.com/AVfFAHdG

Identifying hackable Switch units: https://ismyswitchpatched.com
How to set up emuNAND: https://pastebin.com/iVLBhpPp
How the Switch prevents downgrading using eFuses: http://wololo.net/2017/08/24/nintendo-switch-prevents-downgrading
How to update and downgrade without burning eFuses (ChoiDujourNX): https://gbatemp.net/threads/513416

Play Switch online with /hbg/ (For Free!)
https://github.com/spacemeowx2/switch-lan-play/blob/master/README.md#usage
/hbg/ US Server frog-skins.com:11451
/hbg/ EU Server switch.lan-play.com:11451

Scene releases: http://nswdb.com
Game card dumping tool: https://gbatemp.net/threads/508343
SD to .nsp dumper: https://gbatemp.net/threads/514816
System updates for ChoiDujourNX: https://darthsternie.net/index.php/switch-firmwares
JKSV (save backup tool): https://gbatemp.net/threads/516186
Checkpoint (also a save backup tool): https://gbatemp.net/threads/503899
DevMenu NSP (FW 6.x and higher only): https://share.dmca.gripe/tfNVpfFB9xB67n7D.zip
.xci to .nsp converter: https://gbatemp.net/threads/515341
.xci installer (makes them work like .nsps): https://gbatemp.net/threads/518173
FTP tool to transfer files without removing the SD card: https://github.com/WinterMute/ftpd/releases
Overclocking in Retroarch for better N64 and PS1 emulation (might hurt the console's battery): https://boards.fireden.net/vg/thread/236708320/#236712714

Alternative guide (achieves the same result as the "start here" guide): https://switch.homebrew.guide
SX guide: https://pastebin.com/3pCcL1PR
SX license crack: https://gbatemp.net/threads/582831


NEWS
News from June 2019 onwards: https://pastebin.com/4Dr3NxsS
Switch news from June 2018 to September 2019: https://pastebin.com/VtwqNqSy


FAQ
Q: How do I hack my Switch?
A: You have two options. Check out Hekate or any of its variations (free, can be used to install .nsp games) and SX (paid, can run .xci files and install .nsp files) in the links above if you wish to know more or if you need a guide. Use devmenu to install DLC .nsp files.

Q: Can I get banned from online services?
A: You will get banned if you play online with games you don't own or if you install NSP files.
You can also get banned for doing something stupid, such as using DevMenu to set a custom avatar, which would be impossible for a regular user.
Disabling telemetry (as far as Nintendo lets you do it) is recommended.

Q: Is it possible to mod Switch games?
A: You can do so using LayeredFS, a tool to apply mods without altering the actual game.