Dump multiple databases:
mysqldump -u root -p --databases db1 db2 db3 >dump.sql
Dump some selected tables:
mysqldump -u mysqlusername -p databasename table1 table2 table3 > databasebackup.sql
Dome all tables except some tables:
mysqldump -u username -p database –ignore-table=database.table1 –ignore-table=database.table2 > database.sql