An incomplete list of shortcuts can be found at [[Wikipedia:Shortcuts]],
and as expected this page has itself various shortcuts like
[[WP:WP]], [[WP:CUTS]], or just [[WP:]].
Other shortcuts for shortcut lists are [[WP:WPR]]
with some [[Wikipedia:Project shortcuts]] and
[[WT:WT]] with some
[[Wikipedia:Shortcuts to talk pages]]. Obviously
many shortcuts are (ab)used to make a [[WP:POINT]]
and best described by [[WP:WOTTA]].
On [[m:|Meta]] shortcuts start with '''WM:''', the list is at [[m:WM:WM]]. As shown, links to shortcuts on other projects work as expected, but redirects (incl. shortcuts) to pages on other projects won't work - this former feature was abused and hence it has been disabled.
Use special pages to find uncategorized or unlisted pages starting with a given prefix, e.g. [[Special:Prefixindex/CAT:]] for some category shortcuts.