Let's hope this is just the first of many dominos to fall.
Here's what you can do to help:
1. Don't publish in overpriced journals. 2. Don't do free work for overpriced journals (like refereeing and editing). 3. Put your articles on the arXiv before publishing them. 4. Only publish in journals that let you keep your articles on the arXiv. 5. Support free journals by publishing in them, refereeing for them, editing them... even starting your own! 6. Help make sure free journals and the arXiv stay free.
Of these, only #5 and #6 take any real work.
For more information start here, and try some of the links: