Platforms

Skinning Forum Official place to talk about and share your skins.
r/OsuSkins subreddit Reddit community centered around skinning.
skinship Discord server Our Discord server!

Skin Collections

Completed Skins Compendium An easy to search archive of all osu! skins posted in the Completed Skins forum.
Circle People Pro Player Skin Collection An outdated collection of skins used by pro players.

Programs and Tools

ImageMap Editor WYSIWYG editor for creating BBCode ImageMap tags.
Image Scaler A small tool to mass-scale images, by default setup to create SD files from HD files.
Fringe Remover Fixes issues with skin assets that may result in white fringing due to osu!'s rendering.
Skin Checker An overview over the progress of your skin, detector for assets that do not do anything, as well as a skin.ini editor.
Mania Column Centering ColumnStart calculator to easily center mania playfields for any aspect ratio.
pinga Filesize Optimiser
Bulk Rename Utility Mass file renamer
Advanced Renamer Mass file renamer
waifu2x AI-powered image upscaler & denoiser focused on anime imagery.

Miscellaneous

Skinnable Files List Spreadsheet containing information about all skinnable images, sounds aswell as all skin.ini commands
Default Skin Complete copy of the default osu! stable skin
Japanese Text on the Default Skin All of the japanese text that is used within the default skin

Templates

Song Selection Template Pixel perfect templates for the song selection showing all the little details for various aspect ratios
Menu Background Template Pixel perfect templates for the menu background showing all the little details for every menu
Galvit's Template Skin THE template skin, containing a template for every asset with information on overlaps, anchor points and much more!
XetThe’s Slate (open source osu! skin template) An open source osu! skin template designed to make skinning easy
skin.ini Template Example skin.ini containing all default values and some helpful links