Following are some useful Unix/Linux commands which are helpful if you are dealing with large sites (files and db size). I find these really handy when moving sites from one server to other, taking backups of Files, Database etc.
Note: To get access to the Unix command line, you will need an SSH client (e.g. Putty). You can also use WinSCP if you are not comfortable with Command line. WinSCP has a feature to enter custom commands using its interface.
Please add other command-line commands that you use while setting up, developing and managing your Drupal sites.
Zip Contents of current directory
zip -r zipfile.zip *
Unzip Contents into current directory
Unzip (and extract) the tar'd, gzipped archive (tarball) Contents into current directory
tar zxvf tarballfile.tar.gz
Remove a directory and its contents (Use with extra care)
rm -rf directoryname
mysqldump dbname -uUSERNAME -pPASSWORD --host HOST > filename.sql
mysql -u root -p[root_password] [database_name] < dumpfilename.sql
Copy all files / directories from one server to other (Both servers should have SSH Support)
rsync -avz --progress username@servername:sourcefolder destinationfolder