There are few different things to follow. You can mark some post as spam (please see the read flag icon), you can mark a person as a spammer (if you are sure it's spam please always do it, you need to go in person's ID to get to the personal profile page, also look for a red flag) and you can do "vote to remove" as Mark suggested.
Now — attention! — a new feature: there is
new special message board we use to report spam and abuse:
http://www.codeproject.com/Forums/1652005/Spam-Watch.aspx[
^].
To get there from any page, you need to do the following: [Main Menu] => "Help" => "Bugs and Suggestions" =>
http://www.codeproject.com/Forums/1645/Site-Bugs-Suggestions.aspx[
^]; on this page, locate "
Spam and abuse watch forum" about the top of the page.
—SA