Here is a dirty script to rename a mysql database or table from command line. Dont for get to stop mysql service!
cd /var/lib/mysql/
/etc/init.d/mysql stop
# rename database...
mv olddbname newdbname
# ...or table
cd database/
mv oldname.frm newname.frm
mv oldname.MYD newname.MYD
mv oldname.MYI newname.MYI
/etc/init.d/mysql start