I’m not really in a position to track and write about every development in the world of ransomware. (Rather, I’ve concentrated on information on specific families and pointers to useful information and advice.)
If a regular timeline is of use to you, though, David Balaban contacted me about his Ransomware Chronicle, which tersely flags ‘New ransomware released’, ‘Old ransomware updated’, ‘Ransomware decrypted’ and ‘Other important events’. No links to further information, though, at time of writing. He also provides ransomware reports for Tripwire’s State of Security blog.