Console scripts are Spellscript scripts that may be run from either the server console or as a player while in-game. The command syntax is ss <script name> <args>, where args is a list of script-dependent arguments. Like all commands, 'ss' must be preceded by a '/' if run as a player.
Additionally, console scripts may be created and edited in-game by use of ss edit <script name>, which brings up the Spellscript IDE loaded with the contents of the desired script. edit is itself a console script, which may be altered to control script editing permissions. (By default, all Ops have script editing access.) If the title of the script is altered when the IDE is closed, it will save as a new console script rather than overwriting the old one.
Hack/Mine comes with a growing set of default console scripts: see the contents of 'sslib' for details. (This is located next to server jar. An 'sslib' also exists in the .minecraft directory for the client, but as of this writing, it is unused since console scripts are currently SMP only.)