Mods: shortcut command line:
Correctly installed mods will appear in your Steam games window. Shortcuts to Source based mods can be created by right clicking on the mod name in the Steam games window and selecting "Create desktop shortcut". shortcut will then be created on your desktop, which you can then move to your start menu or other location as desired.
Maps: shortcut command line:
"..\Steam\Steam.exe" -applaunch 220 +map [map name] +skill 3
Skill: 3 (hard), 2, 1 (easy).
Maps: shortcut command line example:
"C:\Program Files\Steam\Steam.exe" -applaunch 220 +map leonHL2_1 +skill 3
Note that -console can be added to the command line to enable the console, -novid can be added to skip startup videos and +sv_cheats 1 can be added to enable cheats. See this page for more command line options. The order of the commands is not important.
Maps: Episode 2: shortcut command Line:
"..\Steam\Steam.exe" -applaunch 420 +map [map name] +skill 3