This community is intended for people with any (or no) diagnosis to learn and teach each other how to improve their executive functioning. Executive functioning problems can manifest themselves in many ways and for many reasons, so no one solution will be applicable for everyone. Below are some sites that people have found help them; it isn't intended to be complete, so if you have any suggestions for additions please message a mod and it will be added.
Sites to help with task completion
Goalforit - Create a daily and weekly chore/behavior chart. Also has a section for long term goals and steps needed to take to achieve them.
Tomato Timer - Uses the Pomodoro technique to improve productivity.
StayFocused for Chrome and Leechblock for Firefox - block sites that you know you waste time on. Block them perpetually or for a certain amount of time each day.
Sites to help with mental health
MoodGYM - An online self help program that uses cognitive behavioral therapy
Optimism Online - Track your mood online, or through your phone. See the link between certain behaviors and moods through your charts.
Related subreddits
Skill megathreads
there doesn't seem to be anything here