I've not used this - if you have, let me know and I'll add your comments. Has free and premium services, tracks nutrition as well as training.

The importance of a training log, which includes a list of logging applications and web sites
SportTracks - The best training log, with extensible functionality via plugins. This is my top recommendation for serious runners.
Dailymile - This is my top pick for social logging. Casual runners can use this site as their only training log, or combine it with SportTracks fir more sophisticated analytics.

TrainingPeaks

See Also