This is just a list of element14 leaderboards I have found - I will try to keep the list updated as I find more. If you find others, please link them in the comments below.
/leaders/participation-leaderboard
/members-area/leaders/members-area-activity
/challenges-projects/design-challenges/pi-fest/leaders/pi-fest-leaderboard
/challenges-projects/project14/555timermadness/leaders/555-timer-leaderboard
/challenges-projects/design-challenges/twist-turn-and-move-design-challenge-with-te-robotics/leaders
/challenges-projects/design-challenges/at-the-core-design-challenge/leaders/at-the-core-leaderboard
/challenges-projects/project14/rfidnfc/leaders/project14-rfid-nfc-leaderboard
/challenges-projects/project14/hacktheholidays/leaders/hack-the-holidays-leaderboard
/challenges-projects/design-challenges/sci-pi-design-challenge/leaders/pi-sci-leaderboard