I have delivered couple of workshop on umbraco Basics .
And I have work for more then 3+ Years on Umbraco and have work on more the 18 site during this duration.
I am also having 7+ years of experience in Microsoft technology.
And in addition , I have done many type customization in umbraco so of the basic are listed ,
1) Added a new custom session for direct entry in umbraco DB
2) Created custom umbraco page
3) have modify Core umbraco source code for adding user defined language.
and many more.