I also like Strava. It's a good way of keeping in touch with running/cycling friends who you don't see often. The flybys is great (though a wee bit stalkerish!) and have actually made a couple of good friends in other parts of the country by following them on Strava after bumping into them on runs whilst on holiday.

I don't like the way it rounds down though! If you run 9.99 miles it tells you it was 9.9, not 10! (and yes, I'm a bit OCD!)