They are still working as long as you do it carefully, slowly and in the right way... Choose some that are still working and start posting UNIQUE content!!!
Yes web 2.0 still works in SEO .. .. we need to regularly post articles related to our business in these web 2.0 sites and drop a link of our website at the footer so when goggle crawls it , leads to increase in our PR rank. Its a DO FOLLOW link.
Yes, this technique is still working in SEO, write fresh and high quality content relevant to the topic, insert authority links in the content with images and publish in high quality web 2.0 blogs.