It would be great to get notifications for projects and contests that catch your eyes - which is why the awesome bookmark feature has been made available to users with a paid membership plan. Bookmarking can be useful if you want to go over a project at a later time.
To bookmark a project, go to its page, and click the bookmark icon next to the project status.
Alternatively, you can bookmark projects on the Browse Projects page. Just click the bookmark icon next to your preferred project.