To get the URL for your deployed site at meteor.com use the command (you may need to provide your site password if you password protected it):
meteor mongo --url YOURSITE.meteor.com
Which will return something like :
mongodb://client:[email protected]:27017/YOURSITE_meteor_com
Which you can give to a program like mongodump
mongodump -u client -h sky.member1.mongolayer.com:27017 -d YOURSITE_meteor_com\
-p PASSWORD
The password is only good for one minute. For usage:
$ meteor --help mongo