These links may be created as shortcuts via buttons or simply kept FYI. It certainly helps having direct links to certain things as it saves time vs. clicking through the entire interface.
_layouts/user.aspx – manage users for site
_layouts/settings.aspx – site settings
?contents=1 – what web parts are open on the page? Example http://intranet/pages/default.aspx?contents=1
_layouts/create.aspx – page to create content. This is especially useful if you have a funky problem with Silverlight.
_Layouts/AreaWelcomePage.aspx – Welcome page settings
_layout/addgallery.aspx – direct link to Silverlight creation page.
_admin/CNTDBADM.aspx – manage content databases. This link needs to be executed in the central administration web application.
_layouts/viewscopes – view search scopes. This link needs to be executed in the central administration web application.
/_catalogs/users/simple.aspx – User information list for all users in SharePoint. Especially useful when you have funnies in user info. Delete the user from this list, re-add them to SharePoint and most of the issues should be resolved.
Generalapplicationsettings.aspx – Central Administration – General application settings. Obviously also to be executed in the central administration web application.
_admin/ServiceApplications.aspx – Central Administration – Service Application settings. Also to be executed in the central administration web application.
_layouts/storman.aspx – Storage metrics for your SharePoint site.