Most Popular Ubuntu / Linux Posts Of 2009 [Part 1]

After the most popular "Multi-Platform" posts of 2009, here are the most popular Ubuntu & Linux posts - part 1 (because there are so many - but don't worry, I'll only post 2 parts). Please note that obsolete / not very up to date posts such as how to install Firefox 3.5 in Ubuntu Jaunty have been skipped (for articles which are still very useful).