Bassel Bassel Khartabil - an open source software contributor to projects such as Creative Commons & Mozilla has been unjustly detained for nearly four months without trial or any legal charges being brought against him.
Read more & sign the support letter:
http://freebassel.org/
ps: Help get this on the frontpage of HackerNews
I don't think signature campaigns will do any good since not even pressure from the US and Turkey has slowed down the bloodshed so do we really think they will care about a bunch of virtual signatures collected online?
There's a few more viable options that should be considered:
1) Leverage someone who has influence with the Syrian government to take up the cause. Given Bassel has been an open source contributor, maybe look at which tech companies are still contracted by the Syrian government and try to get them to lend a voice of support. Make sure to play up the positive PR that releasing Bassel will have on improving Syria's image.
2) Stop collecting signatures and start collecting money to work the back channels. Let's be honest here, corruption is rife (high corruption index on Transparency International study) and the situation pretty chaotic, if you really want to free Bassel, consider a pragmatic approach.