- Apterous, an online game from the same people that run this site.
- The Countdown Page, Mike Brown's encyclopaedic record of Countdown scores and miscellany.
- The Countdown Database, detailed statistics and round-by-round details of over 5,700 episodes.
- FOCAL, regular in-person events that anyone can enter.
- C4Countdown, Countdown's main online forum, populated by many past octochamps.
- Quantum Tombola, a numbers game solver designed by Graeme Cole.
- A mobile version of the above.
- Greem, a website listing nearly all co-event scores.