Adding a user Contol in a master page is quite easy and is useful too. I have once added the control in the master page for changing the links in quick launch bar and once, for creating a custom footer in the master page .

I have added a post at my new website with detail screenshots which explains the procces to add a link in the master page with user control. Please see the link below.

Add user control in sharepoint master page

I have moved this Post to my new blog which includes n example as well. Please click below.

Impersonation in Sharepoint (RunWithElevatedPrivileges)

I have moved this post to my new blog. Please click SharePoint 2007 Object modelto see the Post.

You can also check SharePoint 2010 Object model at
SharePoint 2010 Object Model

Getting Started With Workflows:

I have moved this Post to my New blog. Please Click at the below link

Getting Started With Workflows