Not something big or important, but I just tried several ways to get tidy library on my Ubuntu box, and none other then this worked. Might save some searching to others.
sudo apt-get install php5-tidy
Tidy is recommended for running SilverStripe (not required).
php5 comes with Tidy library preinstalled but it has to be compiled –with-tidy which is sometimes skipped (well, on the box I’m setting up for example).