Strava
Strava is a social network for cyclists, or really just a competition to be fastest over various segments. You create segments, and then see how you perform both against your previous rides and everyone else. It also works well for finding routes in different places - if someone's done a ride, then chances are the route is interesting.
However Strava offers no way to download the routes or segments so you can see them on your Garmin and follow them easily, you have to go to Bikeroutetoaster and copy out the route manually. To fix this I've written a Greasemonkey User Script which exports the current sgement or ride to a GPX file suitable for using as a "saved ride" in your Garmin 705 or 800.
The Script
You can download and install the Greasemonkey script strava_gpx_exporter.user.js and this will then add a new User Script Command of Download GPX If you're on a strava Ride or Segment page, downloading the whole ride or segment to a GPX file which you can then save to your Garmin Saved Rides folder and then add it to the map or follow it through navigation in the "Where To" setting.
It only works on the http://app.strava.com/rides/1405012 (rides) or http://app.strava.com/segments/629896 (segments), and is based on the actual URL - so you need to use Go to segment page to get an actual segment.
Cosmo Catalano reported a bug to me (actually I'd just uploaded an old version of the script as I'd alredy fixed that bug in the version I was using) so I've fixed that and updated the script on the site. He's also got a webservice version that he's written which is easier to use (but won't do private segments/rides).