No competitor of LetsRun, which neither has a workout log nor a running calculator---that I know of---Merv's Running is part of the history of this site in that it used to host a competitive running forum that drew many of the personalities that migrated to LetsRun in its early days. The Merv forum is no more (and my headaches count is thankfully much lower thanks to that), but the log and calculator persist, with code basically unchanged since 1987, and still a stubborn, if small, base of users.
It's now at mervsrunning.com.