$ mongo
> help
  db.help()                    help on db methods
  db.mycoll.help()             help on collection methods
  sh.help()                    sharding helpers
  rs.help()                    replica set helpers
  help admin                   administrative help
  help connect                 connecting to a db help
  help keys                    key shortcuts
  help misc                    misc things to know
  help mr                      mapreduce

  show dbs                     show database names
  show collections             show collections in current database
  show users                   show users in current database
  show profile                 show most recent system.profile entries
                               with time >= 1ms
  show logs                    show the accessible logger names
  show log [name]              prints out the last segment of log in memory,
                               'global' is default
  use db_name                  set current database
  db.foo.find()                list objects in collection foo
  db.foo.find( { a : 1 } )     list objects in foo where a == 1
  it                           result of the last line evaluated;
                               use to further iterate
  DBQuery.shellBatchSize = x   set default number of items to display on shell
  exit                         quit the mongo shell
> exit