Post your intention to want to work for a startup here: https://www.facebook.com/groups/BerlinStartupJobForHire/
Read job postings here: https://www.facebook.com/groups/BerlinStartupJobs/
General startup stuff here: https://www.facebook.com/groups/159595270791268/
And my previous employers are hiring some senior level Javascript and iOS devs - http://www.6wunderkinder.com/en/jobs