Run this one-liner in your Magento root to have the instaled DB dumped to the directory above with the filename the same as the dbname[.sql]
grep 'user\|dbname\|pass' app/etc/local.xml | tr -d '\n' | sed 's/<username><\!\[CDATA\[\(.*\)\]\]><\/username>.*<password><\!\[CDATA\[\(.*\)\]\]><\/password>.*<dbname><\!\[CDATA\[\(.*\)\]\]><\/dbname>/ mysqldump -u\1 -p\2 \3 > ..\/\3.sql/g' | sh