Campaigns
I think these are or have been worth supporting.
Petition against the Microsoft Office format as an ISO standard
This would not be a technical standard, but a political one. This standard would actually make the world less free, since it is by design impossible to implement this standard properly.
It is worth noting that Microsoft seems to be actively “encouraging” (a.k.a. bribing) partner companies to participate in the national ISO voting processes. This ISO vote is becoming a farce very quickly.
Data Retention Petition Campaign
Data retention is no solution. Petition launched by European Digital Rights (EDRI), supported by numerous organisations.
Petition Against Software Patents
Boycott the Music Industry
Freedom of information is no crime. Boycott initiated by the Chaos Computer Club (CCC).