The Free Software Foundation Europe (FSFE) launched the campaign Public Money? Public Code! for signing their Open Letter. They are addressing you. And the group of you. You over there as well, yes, you.
Being tax payers like everyone, we should all advocate for spending tax money for open source software. Or in our special case: We should campaign for using open source CMS to build public sector web sites. The enhancements and further development that usually are side-effects of such project will again be for the benefit of us all. On the other hand, public authorities benefit from ready-to-use solutions. That is: they can save money. Tax payers' money.
Quote from the Open Letter:
We need software that fosters the sharing of good ideas and solutions. Like this we will be able to improve IT services for people all over Europe. We need software that guarantees freedom of choice, access, and competition. We need software that helps public administrations regain full control of their critical digital infrastructure, allowing them to become and remain independent from a handful of companies.
What we can do? Sign the Open Letter and spread the word. Very easy. And free.