Oracle database:
http://arjudba.blogspot.com
http://kamranagayev.wordpress.com
SQL Server:
http://technet.microsoft.com/en-us/virtuallabs/cc164207
http://www.sqlserverclub.com/pdfs/how-to-install-sql-server-2008-a-step-by-step-guide.pdf
UNIX/LINUX command line:
http://www.pixelbeat.org/cmdline.html