I've heard a lot of people talk about how much they love their Nike iPod sport kit, but many have also mentioned hating the Nike Plus site that goes along with it. RUNNER+ is a brand new online social network for runners who don't want to use Nike's site, but do want to achieve more through community and technology.
RUNNER+ provides forums, groups, challenges, run mapping, member tips & advice, videos and more. If you use systems such as the Nike+ iPod Sport Kit or Garmin Forerunner, then you will benefit even more because it is compatible with those systems. However, if you don't use either you can also enter your data by hand, which means if you run on the treadmill and want to keep track of your data, you can.
Creating an account is free and only takes a minute. Once you login you can synchronize your run data (this step is not required), then you can do things such as download your run data in Excel/CSV format, change your run data, view your data in a boatload of charts, compare your run data to your friends and more.
Try it out and let me know what you think. It seems like the site is still in the beta phase, which basically means it is only going to get better and better with the more people that join.