Since Skrooge 1.1.0, you can add your own source of download for units.
For that, you just have to add a file in $HOME/.kde/share/apps/skrooge/quotes/
This file must be a text file (extension .txt) like this:
#The URL of the source. %1 will be replaced by the internet code of the unit
#The mode (HTML or CSV). In HTML mode, only one value will be extracted from downloaded page. In CSV mode, a value per line will be extracted.
#The regular expression for the price (see http://doc.qt.nokia.com/latest/qregexp.html)
#The regular expression for the date (see http://doc.qt.nokia.com/latest/qregexp.html)
#The format of the date (see http://doc.qt.nokia.com/latest/qdate.html#fromString-2)
dateformat = yyyy-MM-dd
This is not so easy to define regular expression, so you can active Skrooge's traces by doing "export SKGTRACE=1".
Defaults sources are installed in: /usr/share/kde4/apps/skrooge/quotes/