Lickable Menu Bar https://apps.apple.com/us/app/lickable-menu-bar/id6444217677?mt=12 - Classic Mac OS X Menu Bars for macOS
OpenStrip - https://web.archive.org/web/20131104220315/http://www.strout.net/info/coding/macdev/openstrip/ Classic Mac OS Control Strip for early versions of Mac OS X
Classic Menu - http://www.sigsoftware.com/classicmenu/ Restore Classic Mac OS menu bar behavior (not theme, but the behavior) for Mac OS X up to (and including) Mojave (10.14). Does not support Catalina.
mfslives - https://developer.apple.com/library/archive/samplecode/MFSLives/Introduction/Intro.html Apple official sample code for the Filesystem API, allows you to mount MFS (Macintosh File System) images and physical floppy disks.
https://www.macenhance.com/cdock - Customize macOS Dock with like older version themes built in (https://www.deviantart.com/jsteweii/art/Mavericks-783845879 Mavericks theme)
https://github.com/LumingYin/macOSLucidaGrande - Revert font to Lucida Grande (1999-2014 default Mac font)
https://github.com/MoonPadUSer/macOSMavericksTheme - Mojave/Catalina to Mavericks guide
https://github.com/RadratSoftworks/nofun Nofun: Morphin compatibility layer for Android
https://github.com/CounsellorPolonius/mythras - MiniJ compatibility layer for Android
https://gitlab.com/usernameak/brewemulator - Melage, brew compatibility layer for Android
https://www.benvessey.com/mac-old-school - Macintosh System 1-4 icon pack (paid, but provides complimentary commission service)
https://www.softpedia.com/get/System/OS-Enhancements/WinFlip.shtml - Flip 3D
https://archive.org/details/Windows7CursorPack - Windows 7 Cursors
XP explorer: https://winclassic.net/thread/842/windows-xp-classic-explorer https://web.archive.org/web/20230815153706if_/https://cdn.discordapp.com/attachments/503114322617040900/817745326953857024/Classic_Explorer_XP.zip
Windows XP network activity indicator - https://www.itsamples.com/network-activity-indicator.html
Windows XP login shell - https://winclassic.net/thread/1643/xpls-fork-cls2-xp-enthusiasts
Windows XP Freecell and MS Hearts - http://redirect.viglink.com/?key=71fe2139a887ad501313cd8cce3053c5&subId=6513581&u=https%3A//drive.google.com/open%3Fid%3D1v8CaH9KlcPW4YQIygDWNnF5qfMUXJ5kU (Windows 98 PLUS! Spider Solitare included, as well as minesweeper, Solitare, and Spider Solitare from Windows XP which is already included in the list)
https://devodev.itch.io/diskclick - Old HDD clicking sound simulator
https://winclassic.net/thread/1856/windows-xp-x64-sysdm-cpl - XP System Properties
https://bit.ly/WinMP9 - Windows Media Player 9
XP event viewer - https://winclassic.net/thread/930/classic-event-viewer
XP remote desktop - https://winclassic.net/thread/1905/windows-xp-x64-remote-desktop
Outlook Express 6.0 - https://winclassic.net/thread/28/outlook-express-newer-windows-releases
HyperTerminal - https://winclassic.net/thread/864/installing-hyperterminal-windows-vista (still works on Windows 11)
XP Battery Meter (laptops only for obvious reasons) - https://winclassic.net/thread/1280/xp-battery-meter-modern-windows
Older Winvers - https://winclassic.net/thread/891/change-winver-windows-2000-style
XP ACL Editor - https://winclassic.net/thread/1238/acl-editor-xp-modern-windows
https://winaero.com/play-shutdown-sound-windows-10/ - Re-enable shutdown sound on Windows 10/11
"Demetrofication"/"Defluencing" of the Windows 10/11 taskbar menus: https://winclassic.net/thread/1652/list-metro-ified-components-windows (while the early Windows 10 design is called MDL2 technically, Metro only refers to the Windows 8.x interface)
https://winclassic.net/thread/1089/enable-game-explorer-on-windows - Game Explorer re-enable
Vista Network Indicator - https://www.deviantart.com/laushung/art/Network-Activity-Indicator-205863269
Vista/7 UAC: https://winclassic.net/thread/1778/non-xaml-uac-back
Disable rounded corners on W11 to look like W10 - https://windhawk.net/mods/disable-rounded-corners
Restore Windows 8 center titlebar - https://windhawk.net/mods/center-titlebar
Restore 7, XP/Classic, and 8.x caption buttons - https://winclassic.net/thread/2186/dwm-windows-frame-hooking-mods?page=2#:~:text=%2D%20Restore%20Windows%207,the%20classic%20theme.
Control Panel Restoration Pack - https://winclassic.net/thread/1779/restoring-control-panel-applets-links
Restore Windows pre-7 Disk Pie Chart - https://winclassic.net/thread/2077/restore-disk-pie-chart
Windows 7/Vista Colors page - https://winclassic.net/thread/2125/windows-vista-control-panel-colours
Mac OS X Cursors: https://www.deviantart.com/razcalinside/art/Mac-OS-X-Cursor-Pack-27470598
Ubuntu "Human" Cursors: https://www.deviantart.com/nordlicht/art/Ubuntu-Human-Cursors-35930998
Vista Boot Screen for Windows 11: https://www.youtube.com/watch?v=k9CGtPcCLgs
XP Boot Screen for 11: https://www.youtube.com/watch?v=7LfkmIJb4VU
Android 4.0 "Ice Cream Sandwitch" Launcher, Live Wallpaper, Clock widget, Sounds - https://www.mediafire.com/file/w4djsfvzbdjqitc/Android+4.0+ICS+Launcher+++Android+4.0+(ICS)+and+4.4.4+(KitKat)+Icons+And+Live+wallpapers+++Clock+Widget+++Android+4.0+ICS+sounds.7z/file
Android 4.4.4 "KitKat" Launcher, Sounds - https://www.mediafire.com/file/1i5tzmopege15h5/Android+4.4.4+(KitKat)+Launcher+++Sounds+++Icons+++Wallpapers.7z/file
Android 5.0 "Lollipop" Launcher, Sounds - https://www.mediafire.com/file/occm6qe7ecozu2a/Android+5.0+(Lollipop)+Launcher+++Icons+++Wallpapers+++Sounds.7z/file
https://files.catbox.moe/h1y5vp.apk - Espier Browser (iOS 6-style Safari)
https://github.com/autc04/executor - Compatibility layer for Classic Mac OS apps on modern macOS and Linux
https://github.com/icculus/2ine - Run simple OS/2 apps in Linux